UC-NI 


liilit 


GIFT   OF 


PLAIN    DIRECTIONS 


FOB 


THE  CONSTRUCTION  AND  ERECTION 


LIGHTNING-RODS, 

BY  JOHN  PHIN, 

EDITOR  OF  THE   "YOUNG    SCIENTIST,"    AND    THE    "AMERICAN 
JOURNAL  OF  MICROSCOPY." 


THIRD     EDITION. 
ENLARGED   AND    FULLY  ILLUSTRATED. 


NEW  YORK: 
THE  INDUSTRIAL  PUBLICATION  COMPANY. 

1879.  -    f 


Copyright  Secured. 


CA 


CONTENTS. 


PAGE 

Preface,  -  -  in 
The  Lightning- Kod  an  American  Invention,  -  7 
Are  Lightning-Rods  Really  a  Protection?  -  -  7 
"What  the  Lightning-Rod  Should  Do,  r  8 
The  Proper  Material  for  Lightning-Rods,  -  9 
The  Proper  Size  of  the  Rod,  10 
The  Best  Form  of  the  Rod,  -  11 
Proper  Arrangement  of  the  Rod  in  Regard  to  the  Building,  13 
Barns,  Ice-Houses,  etc.,  -  16 
Should  Lightning-Rods  be  Painted?  17 
The  Termination  of  the  Rod  in  the  Air,  18 
The  Best  Method  of  Attaching  Lightning-Rods  to  Build- 
ings, 21 
The  Connection  of  the  Rod  with  the  Ground,  -  23 
Hints  to  Persons  Exposed  to  Thunderstorms,  -  26 
Lightning-Rod  Swindles,  •  27 
Hints  on  the  Surveying  or  Examining  of  Lightning  Rods, 

for  Insurance  Purposes,  27 

Appendix— Home-made  Lightning-Rods,      -           -           -  29 


256265 


PREFACE  TO  THE  THIRD  EDITION. 


During  the  six  years  that  have  elapsed  since  this  work  was 
first  issued,  several  important  discussions  have  been  held  in 
regard  to  the  subjects  upon  which  it  treats.  The  author  has 
carefully  followed  all  that  has  been  written  in  connection 
with  lightning  rods,  but  he  finds  no  reason  to  alter  any  of 
his  original  statements  and  directions.  Several  patents  have 
also  been  taken  out  during  the  last  few  years,  but  none  of 
them  present  any  improvements  of  importance,  the  old  and 
well  known  devices  being  sufficient  to  meet  all  demands.  So 
that  it  still  remains  true  that  perfect  protection  may  be  ob- 
tained without  infringing  upon  any  patent. 

The  extensive  demand  which  has  existed  for  this  book  is 
not  the  only  compliment  which  has  been  paid  to  it.  The 
author  of  a  somewhat  pretentious  volume  on  "  Lightning 
Protection,"  has,  with  unblushing  effrontery,  appropriated 
several  of  our  original  illustrations,  and  has  used  his  scissors 
freely  on  the  text,  and  all  without  acknowledgment.  This, 
however,  was  to  have  been  expectod  in  a  book  written  solely 
for  the  purpose  of  advertising  a  worthless  patent.  The  pres- 
ent volume  still  remains,  as  when  first  issued,  the  only  book 
published  on  lightning  rods,  which  has  not  been  written  for  the 
purpose  of  puffing  some  particular  patent. 

The  author  lays  no  claim  to  novelty  for  any  of  the  princi- 
ples laid  down  in  this  little  treatise.  They  are  all  old  and 
well  established.  Many  of  the  illustrations  and  methods  of 
experimental  proof  are,  however,  original,  and  it  is  hoped 
that  they  will  tend  to  render  the  subject  clear  and  easily 
understood,  so  that,  as  we  have  always  claimed,  by  its  aid 
any  intelligent  mechanic  can  put  up  a  lightning  rod  which 
will  not  infringe  any  patent,  and  which  will  afford  perfect 
protection. 

New  York,  May,  1879. 


PREFACE  TO  THE  SECOND  EDITION. 


The  favor  with  which  the  first  edition  of  this  little  work  has  been 
received  induces  the  author  to  make  a  few  additions  of  a  thoroughly 
practical  nature.  These  additions  are  so  important  in  themselves,  that 
he  has  deemed  it  best  to  throw  them  into  the  form  of  an  appendix, 
rather  than  to  incorporate  them  with  the  body  of  the  work. 

The  importance  of  thorough  protection  from  the  effects  of  lightning 
is  very  generally  greatly  under-estimated,  except  perhaps  in  those  cases 
where  the  fears  of  property-owners  have  been  excited  by  the  venders 
of  rods,  whose  chief  excellence  lies  in  the  amount  of  money  which 
their  sale  brings  to  the  manufacturers.  Having  carefully  watched  the 
records  of  the  destruction  of  property  by  lightning  during  several  years, 
we  feel  quite  certain  that  a  good  rod  is  quite  as  important  as  a  fire- 
insurance  policy. 

"While  giving  expression  to  a  well-founded  contempt  for  the  ordinary 
venders  of  lightning-rods,  we  would  by  no  means  be  understood  as 
condemning  all  those  who  are  engaged  in  the  business  of  manufactur- 
ing and  erecting  these  valuable  adjuncts  to  our  houses.  We  are  per- 
sonally acquainted  with  dealers  of  thorough  honesty  and  excellent 
judgment;  and  although  we  may  differ  from  them  in  opinion  in  regard 
to  certain  points,  such  as  the  matter  of  insulation,  terminal  points,  &c., 
yet,  since  we  are  in  perfect  accord  as  to  the  necessity  for  a  substantial 
rod  and  a  good  ground  connection,  we  feel  that  those  who  employ 
these  men  will  not  be  disappointed. 

At  the  same  time,  we  would  reiterate  the  statement  which  has  been 
made  in  the  body  of  the  work,  to  the  effect  that  amongst  the  scientific 
men  of  the  present  day  there  is  no  difference  of  opinion  in  regard  to 
the  general  principles  which  should  govern  us  in  the  construction  and 
erection  of  lightning-rods.  It  is  true  that  in  a  recent  utterance,  Prof. 
Henry,  of  Washington,  whose  scientific  reputation  stands  very  high, 
has  gone  back  at  least  a  century  in  his  views.  Fortunately,  however, 
since  some  of  his  most  important  statements  contradict  the  experience 
of  every  tyro  in  electrical  experimentation,  his  opinions  upon  this 
subject  cannot  carry  much  weight  But  with  this  single  exception,  we 
believe  that  scientific  men  are  in  perfect  accord  in  regard  to  everything 
connected  with  lightning-rods. 

In  this  little  book  we  have  endeavored  to  be  sound  and  reliable, 
and  we  have  not  aimed  at  novelties,  though  perhaps  a  few  new  meth- 
ods of  illustration  and  of  proof,  relating  to  general  principles,  and  of 
arrangement  as  regards  the  rod  itself,  have  been  introduced.  In  a 
word,  we  have  held  steadily  in  view  the  diffusion  of  sound  practical 
information,  and  not  the  manufacture  of  a  reputation  for  brilliancy 
and  ingenuity. 


PREFACE. 


THERE  are  few  subjects  concerning  which  less  is  known  by  the  public  at 
large  than  the  principles  that  should  govern  the  construction  of  Lightning- 
Rods.  Nor  does  this  apply  to  the  mere  public  alone.  The  authors  of  our 
popular  scientific  books,  and  the  editors  of  many  of  those  papers  that  attempt 
to  give  scientific  instruction,  are  equally  at  fault;  their  directions  being  any- 
thing but  accurate.  This  assertion  may  perhaps  be  characterized  as  "  vague  " 
and  "  sweeping;"  but  unfortunately  it  can,  if  necessary,  be  easily  sustained  by 
numerous  pointed  illustrations.  And  yet  the  question  of  protection  from 
lightning  is  confessedly  a  very  important  one,  and  has  engaged  the  attention 
of  some  of  the  most  enlightened  governments  on  earth.  On  several  different 
occasions  has  a  committee  of  the  French  Academy  examined  the  subject  at 
the  instance  of  the  government.  Neither  have  the  British  left  this  question 
unexamined,  as  their  piles  of  Blue-Books  testify.  The  propriety  of  making 
such  earnest  investigations  is  obvious  from  the  following  record:  In  1864, 
Boudin  presented  to  the  French  Academy  of  Sciences  a  table  showing  that  in 
France,  during  the  period  of  29  years,  2,238  persons  were  killed  by  lightning, 
and  6,714  struck  without  being  killed.  It  is  thus  seen,  that,  during  each  of 
these  years,  77  persons  lost  their  lives,  and  232  were  injured.  Among  those 
struck  by  lightning,  between  the  years  1835  and  1852,  67  per  cent,  were  males, 
10  per  cent,  females,  and  23  per  cent,  unknown.  From  1854  to  1863,  26.7  per 
cent,  of  females,  and  73.3  per  cent,  of  males,  were  struck. 

At  sea  the  damage  done  to  shipping  has  been  equally  marked.  A  writer  in 
Nicholson's  Journal  of  the  Progress  of  Science  calculates  the  loss  by  lightning, 
in  Great  Britain  alone,  at  £50,000  sterling  annually,  and  Sir  William  Snow 
Harris  believes  that  this  estimate  is  under  the  mark.  During  the  five  years 
between  1810  and  1815,  the  British  Navy  lost  by  lightning  no  less  than  forty 
sail  of  the  line,  twenty  frigates,  and  twelve  sloops  and  corvettes.  Indeed,  it 
has  been  proved  beyond  all  controversy  that,  in  Europe  at  least,  the  danger 
of  being  killed  by  lightning  is  far  greater  than  the  danger  of  being  killed  by  a 
railroad  accident ;  or,  in  other  words,  that  out  of  the  entire  population  the 
percentage  of  those  killed  by  lightning  is  greater  than  the  percentage  of  the 
passengers  who  are-  killed  on  railroads. 

And  yet,  in  the  face  of  this  melancholy  record,  it  remains  an  undoubted 
truth  that  life  and  property  may,  with  certainty,  be  protected  from  injury  by 
lightning.  There  are  many  instances  where  buildings  furnished  with  rods 
have  been  struck  by  lightning  and  injured;  but,  so  far  as  our  experience 
extends,  the  rods  .have  been  defective  in  every  case.  In  the  British  Navy, 
where  the  very  perfect  system  of  protection  devised  by  Harris  has  been 
adopted,  injury  by  lightning  has  become  a  thing  almost  unknown.  Harris, 
in  his  work  on  Frictional  Electricity,  tells  us  that,  in  the  British  Navy,  damage 
by  lightning  has  happily  ceased,  but  that  in  the  Merchant  Navy,  where  no 


iv  PREFACE. 

adequate  means  are  taken  to  check  it,  it  unfortunately  still  continues.  We 
regard  his  testimony  upon  this  point  as  worthy  of  acceptance. 

In  view  of  these  facts,  it  is  obviously  of  the  utmost  importance  that  the 
public  generally  should  be  fully  informed  in  regard  to  the  principles  upon 
which  lightning-rods  ought  to  be  erected.  It  unfortunately  happens  that  the 
information  given  in  regard  to  this  subject  by  most  of  our  text-books  on 
Natural  Philosophy  is  exceedingly  meagre,  and  as  for  special  treatises— there 
is  not  a  single  one,  now  before  the  public,  in  the  English  language.  It  is 
true  that  we  have  a  few  pamphlets  and  one  small  book  ;  but  they  can  hardly 
be  dignified  with  the  name  of  treatises  on  the  subject,  since  they  are  all 
written  in  the  interest  of  some  particular  patent,  and  were  never  intended  to 
give  such  information  as  would  enable  an  ordinarily  intelligent  mechanic  to 
erect  a  lightning-rod  for  himself. 

In  this  country,  our  people  appear  to  have  derived  most  of  their  information 
from  a  class  of  wandering  mechanics  known  as  "Lightning-Rod  Men."  The 
object  of  these  men,  wo  are  sorry  to  say,  seems  in  many  cases  to  be  to  make 
money  rather  than  to  afford  protection  from  lightning;  and  hence,  in  travel- 
ling through  the  country,  we  often  find  a  vast  amount  of  labor  and  expense 
wasted  on  lightning-rods — in  many  cases  to  their  positive  detriment.  On 
several  occasions  we  have  seen  a  lightning-rod  earned  alongside  the  metal 
staff  which  supported  the  weather-vane,  while  at  the  same  time  it  was  care- 
fully insulated  from  it;  and  it  is  within  our  personal  knowledge,  that,  on 
three  of  the  new  colleges  devoted  to  the  special  culture  of  science,  the  light- 
ning-rods are  carefully  and  expensively  insulated  from  the  building  by  means 
of  glass  insulators.  The  Trustees  of  these  institutions  seem  to  be  unaware 
of  the  fact  that  it  is  the  opinion  of  our  ablest  electricians  that  the  best  way 
to  carry  a  lightning-rod  to  the  ground  is  to  carry  it  down  the  inside  of  the 
house.  The  rods  to  which  we  have  alluded  are  a  standing  satire  on  the 
science  taught  within  the  walls  which  they  have  been  erected  to  protect. 

Almost  all  the  lightning-rods  which  are  sold  by  these  itinerant  vendors  are 
patented;  and  it  may  therefore  be  worth  while  to  remind  our  readers  that 
aU  the  essential  requisites  for  perfect  protection  may  be  embodied  in  a  rod  which 
does  not  infringe  any  patent.  The  issue  of  a  patent  for  any  device  is  no 
evidence  whatever  of  the  value  of  that  device.  Nine-tenths  of  ah"  the  inven- 
tions protected  by  patents  are  perfectly  worthless.  Every  sensible  mechanic 
knows  this.  Many  patents  are  obtained  simply  for  the  sake  of  the  opportunity 
which  it  gives  the  patentee  to  talk  and  argue  about  his  invention.  Indeed, 
a  great  many  of  these  men  feel  a  good  deal  as  did  a  certain  applicant  for  a 
patent,  who,  upon  being  asked  by  the  examiner,  "Of  what  possible  use  can 
such  a  device  be?"  replied,  "  Wall,  I  guess  it  is  gootl  for  me  to  sell  rights  to 
it."  There  is  no  doubt  but  that  all  the  various  devices  of  hollow  rods,  twisted 
rods,  hacked  rods,  and  the  endless  variety  of  plans  devised  for  attaching  rods 
to  buildings,  are  perfectly  childish.  If  you  have  a  good  solid  rod  put  up  with 
the  precautions  which  we  detail,  you  need  not  be  afraid.  You  are  as  sate  as 
any  lightning-rod  man  can  make  you.  That  owners  of  houses  may  in  most 
cases  find  it  desirable  to  employ  competent  mechanics  to  put  up  lightning- 
rods,  we  do  not  mean  to  deny.  But  we  feel  certain  that  a  slight  knowledge 
of  the  subject  would  have  saved  our  house-owners,  and  especially  our  hard- 
working farmers,  thousands  of  dollars  out  of  which  they  have  been  swindled 
by  "  Lightning-Rod  Men." 

NEW  YOKE,  JUNE,  1871. 


LIGHTNING-RODS, 


AND 


HOW   TO    CONSTRUCT  THEM. 


An  American  Invention.— Whatever  differences  of  opinion 
may  exist  in  regard  to  the  authorship  of  the  discovery  of  the  identity  of 
lightning  and  electricity,  there  can  be  none  in  regard  to  the  fact  that 
Franklin,  and  Franklin  alone,  invented  the  lightning-rod;  and,  strange 
to  say,  when  it  left  his  hands  it  was  nearly  as  perfect  as  it  is  to-day. 
Notwithstanding  the  many  patents  that  have  been  issued  for  alleged 
improvements  in  lightning-rods,  we  would  as  soon  trust  our  property  to 
a  rod  constructed  after  the  directions  given  by  the  inventor  as  to  one 
made  according  to  the  latest  devices,  covered  by  the  broad  seal  of  the 
United  States  Patent-Office.  It  is  true  that  during  the  last  half-century 
we  have  learned  something  about  rods  and  their  mode  of  action,  and 
have  acquired  a  more  perfect  knowledge  of  the  special  points  which  de- 
mand attention,  in  the  effort  to  secure  perfect  safety.  But  it  will  be 
found,  on  examination,  that  Franklin's  old  rod  embodies  all  the  points 
necessary  for  a  perfect  conductor,  and  that,  consequently,  we  are  not  at 
the  mercy  of  any  patent-right  monopoly  in  this  matter. 

Are  Lightning-Rods  Really  a  Protection!— There  are 

many  instances  on  record  where  buildings  protected  by  rods  have  been 
struck  and  injured.  But  this  is  not  to  be  wondered  at,  when  we  reflect 
that  fully  one-half — nay,  perhaps  three-fourths — of  all  the  rods  now 
actually  erected,  violate  the  fundamental  principles  upon  which  their 
efficiency  depends.  Besides  serious  errors  in  regard  to  arrangement 
and  continuity,  it  will  in  general  be  found  that  it  is  only  by  the  merest 
accident  that  a  good  ground  connection  is  ever  'Secured.  This  point 
will  be  more  fully  discussed  in  a  subsequent  paragraph.  Meanwhile, 
the  following  facts  prove  irrefragably  the  great  value  of  well-constructed 
rods.  The  Cathedral  of  St.  Peter,  in  Geneva,  although  so  elevated  as  to 
be  above  all  other  buildings  in  the  neighborhood,  has  for  three  centuries 
enjoyed  perfect  immunity  from  damage  by  lightning;  while  the  tower 
of  St.  Gervaise,  although  much  lower,  has  been  frequently  struck. 
This  doubtless  arises  from  the  fact,  that  all  the  towers  of  St.  Peter  are 
accidentally  furnished  with  very  perfect  conductors.  The  great  column 


8  • -L  I<> H  5>rN-'G  -  E  O  D  S. 

of  London  known  as  the  Monument,  erected  in  1677  in  commemoration 
of  the  great  fire,  although  over  two  hundred  feet  in  height,  has  never 
been  struck;  while  much  lower  buildings  in  the  vicinity  have  not  es- 
caped. The  Monument,  however,  is  protected  by  a  most  perfect  con- 
ductor; the  upper  end  terminating  in  a  vase  from  which  proceed 
numerous  metal  plates  designed  to  imitate  the  appearance  of  tongues 
of  flame.  The  vase  communicates  by  means  of  stout  bars  of  iron  with 
the  metal  staircase  which  descends  through  the  middle  of  the  column, 
and  terminates  in  the  ground.  A  ntill  more  striking  instance  of  the 
value  of  lightning-rods  is  a  church  on  the  estate  of  Count  Orsini,  in 
Carinthia.  This  building  was  placed  upon  an  eminence,  and  had  been 
so  often  struck  by  lightning  that  it  was  deemed  no  longer  safe  to 
celebrate  divine  service  within  its  walls.  In  1730,  a  single  stroke  of 
lightning  destroyed  the  entire  steeple;  after  it  had  been  rebuilt,  it  was 
struck  on  an  average  four  or  five  times  a  year,  without  counting  ex- 
traordinary storms,  during  which  it  was  struck  from  five  to  ten  times  in 
a  single  day.  In  1778,  the  building  was  reconstructed  and  furnished 
with  a  conductor;  and,  according  to  Lichtenberg,  up  to  1783,— that  is 
to  say,  during  the  space  of  five  years, — the  steeple  had  been  struck  only 
once,  and  this  stroke  had  fallen  upon  the  metallic  point  without  pro- 
ducing any  damage.  For  two  or  three  years  after  its  erection,  the 
church  of  St.  Michael  in  Charlestown  had  been  frequently  damaged  by 
lightning;  a  conductor  was  attached  to  it,  and  during  the  following 
fourteen  years  it  had  not  been  injured.  The  steeple  of  St.  Mark's  in 
Venice  has  a  height  of  340  feet,  and  was  frequently  struck  by  lightning 
until  a  proper  lightning-rod  was  applied  to  it,  since  which  time  it  has 
not  been  injured.  These  facts  leave  no  room  for  doubt  in  regard  to 
the  great  value  of  lightning-rods. 

What    the  Lightning-Rod  Should    do. — It  is  not  our 

purpose  to  enter  into  an  attempted  exposition  of  the  theories  of  elec- 
tricity, its  phenomena  and  laws.  For  these  we  must  refer  our  readers 
to  any  of  the  ordinary  works  on  Natural  Philosophy.  At  present  we 
propose  to  deal  with  bare  facts,  and  to  give  concise  directions  for  prac- 
tical guidance.  The  function  or  office  of  the  lightning-rod  is  twofold. 
In  the  first  place,  it  acts  as  a  means  whereby  the  accumulated  electricity 
existing  in  the  atmosphere  is  silently  drawn  off,  and  allowed  to  pass 
into  the  earth,  and  thus  prevent  an  explosion;  and,  in  the  second, 
it  acts  as  a  path  by  which  explosions,  lightning  flashes,  or  disruptive  dis- 
charges (as  they  are  more  properly  called)  may  find  their  way  to  the 
earth  freely,  and  thus  be  carried  off  without  any  danger  of  their  acting 
with  mechanical  violence,  as  they  are  certain  to  do  when  made  to  pass 
through  what  are  called  non-conductors.  Experience  teaches  us,  that,  so 
long  as  a  discharge  of  electricity  passes  off  through  a  wire  that  is  large 
enough  to  carry  it  safely,  it  dees  not  cause  any  damage  or  give  rise  to 
the  exhibition  of  mechanical  violence.  A  spark  from  the  prime  con- 


LIGHTNING-RODS.  9 

ductor  of  an  electrical  machine,  if  passed  through  a  moderately  fine  wire, 
does  not  injure  it;  if  passed  through  a  thick  card,  it  will  pierce  it;  and, 
if  passed  through  a  small  block  of  wood,  it  will  rend  it  asunder.  On 
the  occasion  of  every  thunderstorm,  there  is  a  large  quantity  of  elec- 
tricity to  be  conveyed  from  the  clouds  to  the  earth,  through  the  air, 
which  is,  in  general,  a  very  poor  conductor.  This  electricity  always 
tends  to  pass  by  the  easiest  path,  or,  as  electricians  say,  the  line  of  least 
resistance.  The  resistance  of  any  line  may  be  lessened  by  various  cir- 
cumstances, such  as  the  presence  of  hot  vapors,  as  from  chimneys, 
heated  haystacks  in  the  open  field,  or  heated  haymows  in  the  barn ;  the 
existence  of  a  line  of  carbonaceous  matter,  such  as  exists  in  a  column  of 
smoke;  the  presence  of  a  tree  with  its  leaves  and  sap,  or  of  a  house  with 
its  chimneys;  or  the  fact  that  the  air  has  been  rendered  moist  by  the 
passage  of  a  shower  of  rain.  So  difficult  is  it,  however,  to  detect  the 
circumstances  which  render  any  particular  path  more  easy  than  others, 
for  the  electricity  to  follow,  that  we  are  often  unable  to  give  a  reason 
for  its  following  a  particular  course,  and  the  action  of  this  mighty  force 
seems  to  us  like  a  mere  freak.  Such  ideas  are,  however,  entirely  wrong; 
and  we  may  accept  most  implicitly  the  statement,  that  the  flash  will 
always  take  the  easiest  path,  and  it  must  be  our  duty  to  determine 
beforehand  what  this  path  shall  be,  and  to  make  it  so  easy  and  so  per- 
fect that  the  resistance  will  not  cause  the  electricity  to  produce  the 
slightest  mechanical  violence.  And  if  we  do  BO,  then,  just  as  one  may 
hold  in  the  hand  a  slender  wire  while  a  powerful  charge  of  electricity  is 
sent  through  it,  — even  so  we  might  hold  in  our  hands  a  good  lightning- 
rod  at  the  instant  of  its  being  struck,  and  yet  receive  no  injury. 

The  Proper  Material  for  Lightning-Rods.— The  fore- 
going considerations  clearly  show  that  lightning-rods  should  be  made 
of  the  very  best  conducting  material,  and  of  a  size  sufficient  to  carry  off 
the  heaviest  discharge  that  is  ever  likely  to  fall  upon  them.  Of  all  well- 
known  substances,  metals  are  the  best  conductors;  but  even  amongst 
metals  there  are  great  differences  in  this  respect;  some  metals,  accord- 
ing to  Becquerel,  conducting  nearly  75  times  better  than  some  others. 
But,  on  examination,  we  find  not  only  great  differences  in  the  conduct- 
ing powers  of  the  metals,  but  great  differences  in  the  estimates  of  differ- 
ent observers.  Thus  it  will  be  seen  that  Keiss  estimates  the  conducting 
power  of  silver  at  four  times  the  value  which  is  given  to  it  by  Ohm; 
both  estimates  being  referred  to  copper  as  a  standard.  It  must  be 
noted,  however,  that  there  is  a  certain  marked  uniformity  of  result  in 
the  determinations  of  all  these  savans.  They  all  place  gold,  silver,  and 
copper  very  high  in  the  scale;  while  the  values  assigned  to  platinum, 
iron,  tin,  and  lead  are  very  low.  We  may  perhaps  note  that  the  de- 
terminations made  by  Lenz  are,  in  general,  regarded  as  being  amongst 
the  most  reliable.  There  are,  however,  but  two  metals  whose  claime 
are  worth  considering, — copper  and  iron.  The  others  are  too  costly. 


10 


LIGHTNING-KODS. 


The  following  table  gives  the  relative  conducting  powers  of  the  different 
metals  according  to  the  best  authorities: — 

Table  Giving  the  Conducting   Power  of  Metals  for  Electricity. 


METAL. 

NAME  OF  OBSERVER. 

BEC- 
QTJEBEL. 

OHM. 

DAVY. 

LENZ. 

HEISS. 

POOTLLET. 

Copper, 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

Silver, 

73-60 

35-60 

109-10 

136-25 

148-74 

Gold, 

93-60 

57-40 

72-70 

79-79 

88-87 

103-05 

Zinc, 

28-50 

33-30 

Platinum, 

16-40 

17-10 

18-20 

14-16 

15-52 

22-50 

Iron, 

15-80 

17-40 

14-60 

17-74 

17-66 

(15-60 
1  18-20 

Tin, 

15-50 

16-80 

30-84 

14-70 

Lead, 

8-30 

9-70 

69-10 

14-62 

10-32 

Mercury, 

3-45 

2-60 

Potassium, 

1-33 

Brass, 

28-00 

29-33 

27-70 

(  15-20 
\23-40 

Palladium, 

16-40 

18-18 

Cadmium, 

38-35 

Nickel, 

13-15 

Cast  Steel, 

(  13-00 
\  20-50 

Comparing  the  estimate  of  the  different  authorities  given,  we  find  the 
estimated  relative  values  of  copper  andiron  to  vary  between  14. 6  and 
18.2  for  iron  to  100  for  copper. 

It  is  found,  however,  that  different  samples  of  both  copper  and  iron 
vary  very  much  in  their  conducting  powers.  Pure  copper  being  taken 
at  100,  it  will  be  found  that  the  conducting  power  of  even  the  best 
selected  samples  of  commercial  copper  is  less  than  this  by  from  five 
to  15  per  cent. ;  while  the  ordinary  commercial  article  falls  below  this 
standard  by  from  30  to  60  per  cent.  On  the  whole,  we  are  perhaps  safe 
in  taking  the  relative  conducting  powers  of  iron  and  copper  as  one  to 
four.  That  is  to  say,  that,  if  a  rod  of  copper  of  a  given  size  is  found 
to  be  sufficient,  then  an  iron  rod,  to  be  equally  safe,  ought  to  weigh 
four  times  as  much  per  lineal  foot. 

Proper  Size.— Great  differences  of  opinion  exist  in  regard  to  the 
size  of  rod  necessary  to  insure  safety.  The  old  directions  by  the  French 
Academy  of  Sciences,  named  a  rod  of  from  one-half  inch  to  one  inch 
square  as  a  safe  conductor.  The  following  extract  from  the  last  report 
gives  their  latest  views  upon  this  point:  "A  discharge  of  our  electric 
batteries  is  capable  of  melting  several  yards  of  very  fine  iron  wire.  A 
flash  of  lightning  is  capable  of  volatilizing  more  than  one  hundred  yards 
of  bell-wire,  or  of  the  wire  that  is  usually  employed  in  connection  with 
the  hammers  of  public  clocks.  In  1827,  upon  the  packet-boat  New  York, 
a  surveyor's  chain  forty  yards  long,  made  of  iron  wire  a  quarter  of  an 


LIGHTNING-RODS.  11 

inch  in  diameter  which  served  as  a  lightning-rod  on  the  vessel,  was 
melted  by  a  flash  of  lightning  and  dispersed  in  red-hot  fragments.  No 
instance  has  ever  occurred  in  which  lightning  has  raised  to  a  red  heat 
a  bar  of  iron  some  yards  long,  and  four-tenths  of  an  inch  square,  or 
having  a  section  of  one-sixth  of  a  square  inch.  Hence  a  square  rod  of 
iron,  the  side  being  four-tenths  of  an  inch,  has  been  adopted  in  the  con- 
struction of  lightning-rods."  This  shows  that  the  enormous  conductors 
recommended  by  Professor  Henry  and  others  are  unnecessarily  expen- 
sive and  clumsy. 

The  sizes  usually  adopted  have  not  been  determined  by  very  careful 
investigation,  and  cannot  be  regarded  as  safe  guides  in  practice.  Or- 
dinary rods,  made  of  iron,  are  about  half  an  inch  square ;  and  few  cop- 
per ones  are  more  than  equal  to  a  wire  a  quarter  of  an  inch  in  diameter. 
We  are  satisfied,  however,  that  it  is  not  in  size  that  ordinary  rods  are 
deficient,  but  in  continuity,  arrangement,  and  ground  connection.  It  is 
of  the  utmost  importance  that  lightning-rods  should  be  equal  to  any 
demand  that  may  be  made  upon  them  ;  and,  after  carefully  examining 
the  subject,  we  feel  satisfied  that  the  conclusions  reached  by  the  French 
Academy  are  very  nearly  correct.  Instead  of  a  square  rod,  however, 
we  would  recommend  a  strip  or  bar  one  inch  wide  and  three-sixteenths 
of  an  inch  thick,  or,  if  it  were  a  quarter  of  an  inch  thick,  it  would  do 
no  harm.  A  rod  of  the  first-named  dimensions  will  weigh  ten  ounces 
per  lineal  foot.  The  weight  of  the  second  will  be  thirteen  ounces  per 
foot.  If  a  copper  rod  be  used  instead  of  an  iron  one,  it  may  be  made 
much  thinner ;  but  we  could  hardly  recommend  its  reduction  to  the 
fifth  or  sixth  of  the  size  of  the  iron  rod,  as  theory  would  indicate.  A 
copper  rod,  having  the  width  of  one  inch,  should  be  not  less  than  the 
twelfth  or  the  tenth  of  an  inch  thick.  A  rod  of  the  latter  size  weighs 
six  ounces  (.384  Ibs.)  per  lineal  foot. 

The  Best  Form  for  the  Rod.— More  nonsense  has  been 
written  in  regard  to  this  subject  than  in  regard  to  any  other  connected 
with  lightning-rods,  except  perhaps  that  of  insulation.  It  has  been  the 
subject  of  several  patents,  and  has  furnished  an  immense  amount  of 
capital  to  itinerant  venders  of  rods — so  much  so,  that  we  deem  it  neces- 
sary to  present  clearly  the  reasons  which  lead  us  to  beliere  that  the 
efficiency  of  a  rod  depends,  other  things  being  equal,  solely  upon  the 
amount  of  metal  which  it  contains,  and  not  at  all  upon  the  form  that 
may  be  given  to  it. 

If  we  examine  the  rods  ordinarily  found  in  market,  and  puffed  by 
those  who  have  invented  them,  we  shall  find  that,  instead  of  being 
solid  bars  of  a  square,  round,  or  merely  flattened  form,  they  are  tubes, 
twisted  ribbons,  or  bars  whose  cross-section  has  the  form  of  a  star. 
And  if  we  ask  why  these  complicated  and  expensive  forms  have  been 
adopted,  we  shall  be  told  that  it  is  for  the  purpose  of  obtaining  the 
greatest  amount  of  surface  with  the  least  amount  of  metal,  and  this  is 


12 


LIGHTNING-RODS. 


done  because  electricity  always  resides  on  the  surface.  Those  who 
reason  in  this  way,  however,  prove  clearly  that  they  have  never  studied 
the  subject,  else  they  would  be  aware  of  the  fact  that  while  static  elec- 
tricity, as  it  is  called — that  is,  electricity  at  rest — always  disposes  itself 
on  the  surface  of  bodies  charged  with  it,  electricity  in  motion  pervades 
the  entire  substance  of  the  bar  through  which  it  passes,  and  conse- 
quently the  power  of  such  a  bar  to  convey  electricity  is  measured  by 
the  quantity  of  metal  that  it  contains,  and  not  by  the  extent  of  surface 
that  it  presents.  Pouillet  showed  this  in  a  very  clear  and  decisive  man- 
ner. He  measured  the  conducting  power  of  a  fine  wire  of  cylindrical 
form — the  form  that  presents  the  least  possible  surface  in  proportion  to 
its  cubic  contents — and  then,  having  flattened  and  annealed  it,  he  tested 
it  again.  Its  surface  was  enormously  increased,  but  its  power  to  con- 
duct electricity  was  lessened  rather  than  otherwise ;  this  diminution 
being  probably  due  to  the  fact  that  the  wire  was  increased  in  length, 
and,  consequently,  its  cross-section  was  somewhat  diminished.  An  ex- 
periment, equally  decisive,  and  perhaps  somewhat  more  easily  per- 
formed, is  at  the  command  of  every  one  who  has  access  to  a  small  elec- 
trical machine  and  a  two-quart  Ley  den  jar.  Take  a  fine  gold  wire,  say  the 
one-fiftieth  of  an  inch  in  diameter.  This  wire  will  present  nearly  the 
same  surface  as  a  ribbon  of  metal  l-32nd  of  an  inch  wide.  The  wire  will 
carry  off,  without  being  injured,  any  charge 
that  can  be  imparted  to  the  jar.  If,  how- 
ever, we  pass  the  charge  through  a  strip  of 
gold  leaf  having  several  times  the  surface 
of  the  wire,  it  will  be  completely  burned 
up  and  dissipated. 

The  following  very  interesting  experi- 
ment shows  clearly  the  difference  between 
the  action  of  electricity  at  rest  and  elec- 
tricity in  motion,  and  exhibits  also  the  fact 
that  surface  is  of  no  avail  in  carrying  off  a 
charge  of  electricity.  Take  a  Leyden  jar 
of  large  size — say  two  gallons — having  the 
usual  knob  and  other  arrangements,  shown 
in  Figure  1.  In  the  wooden  cover  insert  a 
glass  tube  carrying  at  its  upper  end  a  wire, 
lying  horizontally  across  it,  this  wire  hav- 
ing a  ball  at  each  end,  so  that  the  discharge 
may  take  the  form  of  a  spark  or  an  ex- 
plosion and  not  pass  off  silently.  Between 
the  horizontal  wire  and  the  knob  of  the 
jar  stretch  a  strip  of  gold-leaf  (B),  and 
charge  the  jar  in  the  usual  manner.  So 
long  as  no  discharge  passes  through  the  gold-leaf,  it  will  remain  unin- 
jured,  although  it  is  evidently  charged  as  intensely  as  the  machine  can 


FIG.  1. 


LIGHTNING-RODS.  13 

charge  it.  But  if  we  discharge  the  jar  by  laying  one  ball  of  the  dis- 
charger on  the  outer  coating  of  the  jar  and  the  other  on  the  knob  (A), 
the  gold-leaf  will  be  destroyed.  But  a  wire  the  thirtieth  of  an  inch  in 
diameter,  although  presenting  far  less  surface,  would  have  carried  off 
the  charge  with  impunity.  In  short,  to  end  the  matter,  we  may  state 
that  while  no  flash  of  lightning  has  ever  been  known  to  injure  a  copper 
rod  half  an  inch  in  diameter,  we  have  frequently,  by  artificial  means, 
dissipated  an  amount  of  gold-leaf  that  presented  a  greater  amount  of 
surface. 

The  French  Academy,  although  they  give  no  specific  directions  as  to 
form,  always  speak  of  a  square  rod.  The  well-known  authority,  Sir 
William  Snow  Harris,  in  his  work  on  "  The  Nature  of  Thunderstorms," 
says :  "  Provided  the  quantity  of  metal  be  present,  the  form  under 
which  we  place  it  is  evidently  of  no  consequence  to  its  conducting 
powers,  since  it  would  be  absurd  to  suppose  that  a  mass  of  metal, 
under  any  form,  did  not  conduct  electricity  in  all  its  particles  ;  indeed, 
we  know  that  it  does  so,  and  that  it  is  impossible  to  fuse  by  electricity 
a  portion  only  of  a  homogeneous  metallic  plate  of  uniform  thickness." 
For  ourselves,  we  recommend  the  form  of  a  flat  ribbon,  from  purely 
mechanical  reasons.  A  bar  of  metal  in  this  form  is  more  easily  bent, 
more  conveniently  attached  to  the  building,  and  is  less  conspicuous,  than 
when  in  any  other  form.  Its  conducting  power  is  neither  improved  nor 
impaired. 

Arrangement  of  the   Rod   in  Regard  to   the 

Building. — The  arrangement  of  the  rod  deserves  the  most  careful 
consideration,  not  only  because  upon  it  depends  in  a  large  measure  the 
efficiency  of  the  conductor,  but  because  the  amount  of  metal  used  de- 
termines largely  the  expense  of  the  rod.  The  arrangement  usually 
adopted  consists  in  elevating  from  each  chimney  a  tall  spike,  and  con- 
necting the  several  spikes  or  points  by  rods  which  either  join  the  main 
conductor,  or  descend  directly  to  the  earth.  This  is  very  well,  and  is  in 
accordance  with  the  directions  of  the  French  Academy  of  Sciences,  but 
is  not  quite  as  perfect  as  it  might  be. 

It  is  very  obvious  that  the  most  perfect,  though  not  the  most  economi- 
cal, arrangement  would  be  to  cover  the  entire  building  with  a  sheet  of 
metal.  Then  it  would  be  impossible  for  the  lightning  to  strike  any 
point  without  falling  upon  a  good  conductor.  But  such  an  arrangement 
being  obviously  inadmissible,  we  must  so  arrange  matters  that  the 
most  exposed  points  shall  be  the  conductor  and  its  connections.  With 
this  object  in  view,  the  French  Academy  recommended  the  use  of  rods 
elevated  nine  to  twelve  feet  above  the  building ;  and,  after  a  good  deal 
of  experiment  and  observation,  came  to  the  conclusion  that  a  rod  was 
capable  of  protecting  efficiently  a  space  covered  by  a  radius  equal  to 
twice  the  height  of  the  rod,  above  the  most  elevated  part  of  the  build- 
ing. For  ourselves,  a  very  careful  examination  of  the  conditions  which. 


14  LIGHTNING-RODS. 

arise  during  a  thunderstorm,  leads  us  to  place  no  confidence  whatever 
in  elevated  rods,  and  to  depend  wholly  upon  so  arranging  the  conduc- 
tor that  every  part  of  the  building  shall  be  protected. 

In  a  former  paragraph  we  stated  that  the  lightning  stroke  always 
follows  the  line  of  least  resistance,  and  that  this  line  may  be  deter- 
mined by  the  presence  of  vapor,  smoke,  moisture,  etc.,  forming  ascend- 
ing or  descending  streams  or  horizontal  layers ;  and  it  is  in  this  way 
only  that  we  can  explain  how  it  happens  that  a  house  furnished  with 
very  elevated  conductors,  will  be  sometimes  struck  on  the  gable,  or  why 
a  mast  unfurnished  with  a  conductor,  will  be  struck,  while  a  taller 
mast,  distant  but  a  few  feet,  and  provided  with  a  conductor,  is  not 
struck,  and  evidently  has  not  served  to  carry  off  the  discharge.  If  the 
line  of  least  resistance  were  always  the  shortest  line  mathematically, 
the  rule  of  the  Academy  would  hold  good.  But  let  us  consider  the  case 
of  the  building  shown  in  the  acccompanying  engraving  (Figure  2)> 


FIGURE  2. 

which  represents  a  barn  furnished  with  a  conductor  and  exposed  to  a 
thunderstorm.  We  will  suppose  that  the  barn  has  been  newly  filled  with 
hay,  which  is  giving  off  the  warm  vapor  that  is  pouring  out  of  the  end 
window,  and  forms  an  invisible  band  of  conducting  matter  between  the 
cloud  and  the  barn,  marked  out  in  the  engraving  by  dotted  lines — the 
direction  of  the  wind  being  shown  by  the  arrow.  In  this  case,  the  flash 
will  pursue  the  longer  path  between  c  and  d,  in  preference  to  the  shorter 
one  between  a  and&,  and  the  barn  may  be  set  on  fire,  although  furnished 
with  one  of  the  best  of  rods.  The  same  deflection  of  the  bolt  might 
be  caused  by  rain,  by  a  column  of  smoke,  or  by  the  fact  that  a  part  of 
the  building  had  been  moistened,  while  other  parts  had  been  kept  dry, 
as  frequently  happens  when  the  rain  is  driven  in  particular  directions 
by  a  strong  wind.  In  considering  this  subject,  it  must  be  borne  in  mind 
that  the  flash  does  not  leave  the  cloud  and  pursue  a  sort  of  experimen- 


LIGHTNING-RODS 


15 


tal  path  through  the  atmosphere,  leaping  from  point  to  point  like  a  boy 
picking  his  way  through  a  swamp — now  going  forward,  now  sideways, 
or  sometimes  going  backward  for  the  purpose  of  obtaining  a  new  point 
of  departure.  On  the  contrary,  before  the  slightest  disruptive  action  has 
taken  place,  the  electricity  has,  by  the  power  of  induction,  marked  out 
for  itself  the  precise  path  that  it  will  take,  and  it  pursues  that  path  in- 
flexibly. Every  turn,  every  break,has  been  clearly  defined  ;  and  it  would 
be  of  no  use  to  introduce  into  the  neighborhood  of  this  path  any  good 
conductor,  unless  the  path  itself  were  thereby  electrically  shortened. 
No  additional  elevation  given  to  the  conductor  shown  in  the  engraving, 
and  no  spike  or  spikes  raised  from  other  parts  of  the  ridge  of  the  roof, 
would  have  tended  to  render  this  path  shorter.  But  if  the  conductor 
had  been  simply  carried  along  the  ridge,  and  down  the  edges  of  the 
roof  at  the  gable,  a  way  of  escape  would  have  been  opened,  and  the 
barn  would  have  been  saved. 

In  the  accompanying  engraving  we  give  a  figure  of  a  small  house,  in 
which  the  arrangement  of  the  lightning-rods  is  shown  by  dark  lines. 
It  will  be  seen  that  all  spikes  and  points  are  avoided  as  being  costly, 
unsightly,  and  inefficient,  as  will  be  more  fully  explained  in  a  subsequent 
paragraph,  treating  of  the  termination  of  the  rod  in  the  air.  Each 
chimney  is  surmounted  by  a  cast-iron  cap,  to  which  the  rod  is  attached, 


FIGURE  3. 

and,  after  descending  to  the  ridge,  the  rod  is  led  along  it  in  every 
direction,  and  caused  to  descend  along  the  edge  of  the  roof  at  each 
gable.  It  is  of  course  obvious  that  if  the  building  be  crowned  with  a 
Mansard  roof,  and  finished  with  crestings,  these  will  answer  every  pur- 
pose of  a  lightning-rod  so  far  as  they  go.  But  all  buch  crestings,  as 


16  LIGHTNING-RODS 

well  as  the  waterspouts,  tin  or  other  metal  roofs,  eave-troughs,  etc.,  must 
be  brought  into  metallic  connection,  so  that  the  building  may  form,  elec- 
trically, a  homogeneous  mass. 

A  single  good  rod,  carried  to  the  ground  and  placed  in  perfect  electri- 
cal contact  with  the  earth,  as  hereafter  directed,  is  as  good  as  a  dozen 
rods  We  often  see  a  building  provided  with  several  rods,  all  descend- 
ing into  the  earth.  Such  an  arrangement  shows  great  ignorance  on  the 
part  of  those  who  directed  the  matter.  In  the  first  place,  the  extra 
metal  employed  could  be  used  to  much  better  advantage  by  being  dis- 
tributed over  the  upper  portion  of  the  building  ;  and,  in  the  second,  good 
earth  connection's  are  too  expensive  to  be  needlessly  multiplied.  The 
heaviest  item  of  expense  in  the  construction  of  most  rods  is,  or  ought 
to  be,  the  earth  connection,  if  it  be  properly  made.  One  good  one  is 
amply  sufficient ;  half  a  dozen  poor  ones  are  of  no  use  at  aU. 

It  is  obvious  that  the  rod  should  be  carried  from  the  roof  to  the 
ground  by  the  shortest  possible  way.  Some  have  even  recommended 
that  it  be  carried  down  the  chimney — a  plan  in  which  there  is  nothing 
objectionable,  provided  it  happen  to  be  the  most  convenient. 

BarnS. — Before  leaving  the  subject  of  the  arrangement  of  light- 
ning-rods, it  may  be  well  to  say  a  few  words  in  regard  to  the  peculiar 
conditions  found  in  barns,  ice-houses,  and  similar  structures,  and  the  best 
means  of  protecting  them.  It  has  long  been  known  that  barns,  and 
stacks  of  hay  and  grain,  are  peculiarly  liable  to  be  struck  by  lightning  ; 
and  the  reason  of  this  is  not  difficult  to  discover.  It  rarely  happens 
that  grain  or  hay  is  perfectly  dry  when  put  away,  and  the  peculiar 
character  of  the  atmosphere  that  prevails  during  the  approach  of  a 
thunderstorm  furnishes  just  the  conditions  necessary  to  produce  heat- 
ing or  fermentation,  and  the  consequent  production  of  a  stream  of  dense, 
moist  vapor,  having  comparatively  high  conducting  power.  This 
stream  of  vapor  forms  in  reality  a  conductor  leading  from  the  clouds  to 
the  barn,  or  stack,  but  ending  there — the  very  condition  that  we  should 
seek  to  avoid  ;  for  while  a  conductor  that  leads  past  any  object  is  a  sure 
protector,  a  conductor  that  leads  to  an  object,  and  ends  in  that  object, 
is  an  equally  certain  destroyer.  Our  aim  must,  therefore,  be  to  cause 
any  natural  conductor  that  may  exist,  to  coincide  with  our  artificial 
conductor,  and  unite  with  it.  This  is  best  accomplished  by  furnishing 
all  barns  designed  for  the  storing  of  hay  with  a  ventilator  on  the  ridge, 
and  leading  the  lightning-rod  to  this  ventilator.  Where  there  are  no 
ventilators  but  doors,  or  large  open  windows  in  the  gable,  as  in  the  barn 
shown  in  Figure  2,  the  most  efficient  method  will  be  to  carry  a  stout 
rod  horizontally  from  the  ridge,  for  a  distance  of  two  or  three  feet. 
To  carry  it  vertically  in  such  circumstances  will  be  of  no  use,  as  it  will 
then  be  led  out  of  the  current  of  conducting  vapor,  while  if  it  project 
horizontally,  it  will  be  carried  into  that  stream,  whether  the  vapor 
ascecds  vertically,  or  is  carried  off  in  the  manner  shown  in  our  sketch. 


LIGHTNING-RODS.  17 

Where  ventilators  are  placed  on  a  barn  for  the  purpose  just  mentioned, 
they  should  take  the  form  'of  an  observatory,  or  cupola,  and  the  rod 
should  be  carried  down  at  least  four  sides  or  corners  of  this  cupola. 

Should   Lightning-Rods  be  Painted?— it  is  not 

many  years  since  one  of  our  popular  journals,  whose  main  claim  to 
public  favor  is  based  upon  its  supposed  reliability  in  scientific  matters, 
gravely  informed  its  readers  that  lightning-rods  should  not  be  painted 
because  the  electricity  passed  along  the  surface,  and  to  paint  the  rod 
would  be  to  render  the  surface  a  non-conductor  and  of  course  to  destroy 
the  efficiency  of  the  rod !  And  in  a  circular  published  by  the  well- 
known  E.  Meriam,  of  Brooklyn  Heights, — a  circular  which  was  not 
only  published  in  our  most  widely  circulated  public  journals,  but  was 
distributed  by  the  thousand  by  Mr.  Meriam  himself, — this  idea  is  advo- 
cated. As  Mr.  Meriam's  name  has  been  very  generally  regarded  as  of 
pretty  good  authority,  it  is  no  wonder  that  this  idea  has  in  many  quar- 
ters taken  strong  hold  of  the  public  mind,  and  it  may  not  be  out  of  place 
to  state  the  grounds  upon  which  it  is  regarded  as  erroneous  by  all  scien- 
tific men. 

In  the  first  place,  it  is  an  erroneous  idea  that  it  is  the  surface  alone 
of  a  rod  which  has  the  power  of  conveying  the  electricity.  This  we 
Lave  shown  very  fully  when  discussing  the  proper  size  and  shape  of  the 
rod.  In  the  second  place,  the  surface  of  the  metal  would  remain  me- 
tallic even  if  covered  with  a  dozen  coats  of  paint.  The  fact  is,  that 
every  lightning-rod  is  covered  with  a  coating  of  non-conducting  ma- 
terial, whether  we  will  or  not ;  and  this  material  is  quite  as  good  a 
non-conductor  as  paint !  We  refer,  of  course,  to  the  air  which  of  ne- 
cessity surrounds  every  rod,  and  which  is  well  known  to  be  a  non-con- 
ductor. Even  in  the  case  of  static  electricity,  which  resides  almost 
exclusively  on  the  surface,  it  is  found  that  to  paint  or — what  is  the 
same  thing — to  varnish  the  conducting  surfaces  does  not  diminish  their 
power  to  receive,  retain,  or  convey  a  charge  of  electricity.  All  elec- 
trical apparatus  is  carefully  varnished  with  one  of  the  best  of  non-con- 
ductors,— shellac  varnish.  Even  the  prime  conductor,  which  it  is  desi- 
rable to  keep  in  the  very  best  condition  for  receiving  and  conveying 
electricity,  is  always  thoroughly  varnished  ;  and  this  operation  has  never 
been  known  to  affect  its  efficiency.  Submarine  cables  are  always  most 
carefully  insulated  throughout  their  entire  length,  and  yet  this  opera- 
tion does  not  detract  from  their  conducting  power.  The  truth  is,  that 
arguments  innumerable  might  be  advanced  to  show  that  paint  does  no 
harm  ;  but  the  above  will  suffice.  In  conclusion,  we  would  merely  ask 
the  opponents  of  painting  why  they  are  all  advocates  for  insulation  ? 
It  seems  to  us,  that,  if  a  coat  of  paint  is  sufficient  to  destroy  the  conduct- 
ing power  of  a  rod,  the  insulators  themselves  must  detract  from  its 
efficiency,  since  it  must  be  very  difficult  for  the  lightning  to  dodge 
around  them ! ! 


18  LIGHTNING-RODS 

To  our  readers  we  would  say,  paint  your  rods,  no  matter  of  what 
material  or  of  what  construction.  By  so  doing,  you  will  protect  them 
from  the  influences  of  the  atmosphere,  which  in  the  case  of  some 
metals,  such  as  iron,  is  very  destructive.  Moreover,  you  can  thus 
cause  them  to  resemble,  in  color  at  least,  the  building  to  which  they 
are  attached  ;  and,  as  lightning-rods  can  never  be  an  ornament  to  any 
edifice,  you  will  thus  be  enabled  to  hide  what  would  otherwise  be  a 
disfigurement.  In  a  series  of  directions  by  Professor  Henry,  of  the 
Smithsonian  Institute  of  Washington,  communicated  to  a  gentleman  of 
Boston,  and  extensively  published  by  the  papers  throughout  the  Union, 
it  is  recommended  to  paint  the  rods  with  Uack  paint,  on  the  ground 
[that  such  paint  is  a  good  conductor.  The  alleged  fact  is  not  true,  and 
i  the  directions  are  injudicious.  Black  paint  does  not  conduct  any 
better  than  any  other  paint ;  this  we  have  tested  by  experiment.  To 
attach  a  black  rod  to  a  light-colored  house  would  be  outrageous. 

Termination  of  the  Rod  in  the  Air.— At  an  early 

period  in  the  history  of  the  lightning-rod  attention  was  called  to  the 
rapidity  with  which  points  give  off  and  receive  electricity,  and  also  to 
the  fact,  that  when  a  Leyden  jar  is  discharged  by  means  of  a  sharp 
point,  we  no  longer  have  that  loud  explosion  that  occurs  when  the  ends 
of  the  discharger  are  furnished  with  balls.  Reasoning  from  these  facts, 
Franklin,  with  his  usual  sagacity,  recommended  the  use  of  pointed 
conductors,  and  they  have  been  used  ever  since,  although  at  first  they 
were  most  bitterly  assailed  by  certain  court  favorites  in  England.  This 
famous  discussion,  which  was  known  as  "  The  War  of  the  Knobs  and 
Points,"  ended  in  the  almost  universal  acceptance  of  the  form  recom- 
mended by  Franklin;  and  wherever  lightning-rods  were  used,  they  were 
made  to  terminate  in  points. 

Some  persons,  seeing  that  a  single  point  is  so  efficacious,  have  advised 
that  several  be  used,  upon  the  ground  that  two  points  would  do  twice 
as  much  work  as  one.  Those  who  adopt  this  view  forget  that  the  more 
we  multiply  the  points,  the  more  nearly  do  we  approach  to  the  form  of 
a  ball  or  blunt  rod.  Experiment  shows  very  clearly  that  two  points 
are  not  as  efficient  as  a  single  one,  and  that  the  more  points  we  have, 
the  more  the  conductor  acts  like  a  ball. 

After  all,  however,  the  term  point  is  a  comparative  one.  That  which 
would  be  a  fine  point  when  opposed  to  the  side  of  a  house,  becomes  a 
blunt  rod  when  used  in  connection  with  the  ball  of  a  Leyden  jar.  And 
how  large  may  that  point  be  which  will  bear  to  a  thunder-cloud,  ex- 
tending over  thousands  of  acres,  the  same  relation  which  a  fine  pin 
bears  to  the  knuckle  of  the  human  hand,  or  even  to  the  conductor  of  an 
ordinary  electrical  machine?  Under  such  circumstances,  the  entire 
railings  of  a  Mansard  roof  become,  virtually  a  point ;  and  a  space  equal 
to  that  exposed  by  the  top  of  a  chimney,  is  certainly  small. 

Considerations  such  as  these  have  led  many  of  our  best  electricians  to 


LIGHTNING-RODS.  19 

discard  the  use  of  points,  and  to  advocate  the  adoption  of  blunt  conduc- 
tors, and  even  balls.  Thus  De  La  Rive,  in  his  "  Traite  d'Electricite," 
(Tome  III,  page  161),  speaking  of  the  aerial  termination  of  lightning- 
rods,  says  :  '  We  even  believe  that  a  small  sphere  of  gilt  copper  would 
be  preferable,  for  it  would  resist  more  powerfully  all  destructive  agen- 
cies, and  its  radius  of  activity  would  not  be  much  less  than  that  of  a 
moderately  simrp  point.  It  would  also  have  the  advantage,  that  its 
influence  would  be  exerted  in  all  directions, — an  important  feature  in 
the  not  very  rare  cases,  in  which  the  lightning  strikes  buildings  later- 
ally." The  truth  is,  that  the  point  is  not  one  of  very  great  importance; 
though,  in  regard  to  the  causes  which  induce  lightning  to  strike  build- 
ings laterally,  those  who  have  studied  carefully  the  section  on  the  ar- 
rangement of  the  conductor,  will  be  able  to  appreciate  the  probable 
efficiency  of  a  gilt  ball  in  warding  off  such  strokes. 

The  ablest  and  clearest  exposition  of  this  subject  that  we  have  met, 
is  that  given  by  the  Committee  of  the  French  Academy,  in  their  last 
report  upon  the  protection  of  buildings  from  lightning.  This  commit- 
tee consisted  of  MM.  Becquerel,  Babinet,  Duhamel,  Fizeau,  Edm.  Bec- 
querel,  Regnault,  le  Marechal  V  aillant,  and  Pouillet, — all  names  of  men 
standing  in  the  front  ranks  of  scientific  Frenchmen.  After  describing, 
the  main  features  of  a  well-constructed  lightning-rod,  they  go  on  to  say : 
"  Supposing  a  lightning-iod  to  be  erected  in  accordance  with  these 
conditions,  let  us  examine,  in  a  general  manner,  the  phenomena 
which  would  occur  during  thunderstorms.  The  electricity  developed 
by  influence  in  the  subterranean  water-bed,  instead  of  accumulating 
there,  as  we  have  formerly  described  (when  no  conductor  was  present — 
Trans.\  finds  the  foot  of  the  conductor,  and  rushes  to  escape  by  this 
path  ;  for,  even  in  the  interior  of  a  solid  metallic  bar,  however  long  it 
may  be,  the  electric  fluid  expands  itself  with  a  rapidity  which  may  be 
compared  to  the  velocity  of  light.  It  is  in  this  way  that  the  electric 
fluid  in  the  subterranean  water-bed  is  attracted  by  the  cloud,  and  sud- 
denly accumulates  in  the  upper  part  of  the  lightning-rod.  It  there  pro- 
duces certain  curious  phenomena,  which  it  is  necessary  to  detail. 

"  If  the  lightning-rod  ends  in  a  very  fine  and  sharp  point  of  gold  or 
platinum,  the  fluid  attracted  by  the  cloud  exerts  against  the  air,  which  is 
a  bad  conductor,  a  pressure  so  great  that  it  will  escape,  producing  at 
the  same  time  a  luminous  star,  visible  in  darkness.  The  rays  diverging 
from  this  star  diminish  in  brightness  as  they  recede  from  the  point ; 
they  are  rarely  visible  for  a  greater  distance  than  fifteen  to  twenty  cen- 
timetres. The  air  is  powerfully  electrified  by  them,  and  there  is  hardly 
any  doubt  but  that  these  particles  of  air,  thus  charged  with  fluid  from 
the  point,  that  is  with  the  attracted  fluid,  are  carried  even  to  the  cloud 
itself,  if  the  air  be  calm,  and  thus  neutralize  a  portion,  more  or  less  ap- 
preciable, of  the  fluid  with  which  the  clouds  are  charged.  It  is  this 
neutralization  which  is  called  the  preventive  action  of  the  rod. 

"At  the  same  time  that  the  sharp  point  gives  rise  to  the  luminous  star 


20  LIGHTNING-RODS 

(aigrette),  the  escaping  electricity  often  attains  such  a  degree  of  inten- 
sity that  the  point  becomes  heated  even  to  fusion ;  in  this  case,  gold, 
and  even  platinum  itself,  although  much  less  fusible,  fall  in  large  drops 
along  the  copper  or  iron  to  which  they  are  attached.  When  a  lightning- 
rod  has  thus  lost  its  sharp  point,  and  when  its  upper  end  has  become  a 
mere  large,  fused  button  of  gold  or  platinum,  we  naturally  inquire  if  it 
has  not  been  rendered  useless  ?  This  question  may  be  answered  in  the 
negative,  provided  the  rod  continues  to  fulfill  two  essential  conditions, 
which  are  :  1,  that  it  shall  be  continuous,  and  2,  that  its  lower  extremity 
shall  communicate  largely  with  the  subterranean  water-bed.  In  losing 
its  point,  the  lightning-rod  loses  only  its  preventive  action.  The  star  is 
now  produced  only  under  the  influence  of  a  much  more  powerful  elec- 
trical action ;  and  fusion;  which  depended  chiefly  upon  the  fineness  and 
sharpness  of  the  point,  is  renewe  1  only  with  great  difficulty,  whilst,  at 
the  same  time,  it  leaves  things  precisely  as  they  were  before.  The  air 
is  no  longer  electrified  by  the  star  in  a  luminous  form ;  this  part 
of  the  preventive  action  has  disappeared ;  the  other  part,  that 
which  depends  upon  the  electrifying  of  the  air  by  contact  with  the 
upper  part  of  the  rod,  is  probably  much  lessened.  Finally,  if,  as  often 
happens,  the  electrified  air  from  the  star,  and  from  the  rod  itself,  should 
be  carried  by  the  wind  away  from  the  cloud,  the  preventive  action  is 
often  reduced  to  nothing,  which,  however,  is  not  greatly  to  be  regret- 
ted. The  conclusion  is,  that  in  losing  its  sharp  point,  a  lightning-rod, 
in  reality,  loses  but  a  very  trifling  advantage. 

"  These  considerations  led  the  Commission  of  1855  to  advise  that  the 
upper  end  of  the  rod  be  terminated  by  a  cylinder  of  copper,  eight-tenths 
of  an  inch  in  diameter  and  eight  to  ten  inches  long,  the  summit  being 
tapered  off  into  the  form  of  a  cone  one  and  a  quarter  or  one  and  a  half 
inches  high.  This  copper  cylinder  is  attached  to  the  rod  by  means  of  a 
screw,  and  is  brazed  to  it  so  as  to  make  metallic  contact  certain. 

"  Taking,  now,  for  our  example,  a  rod,  of  which  the  summitis  termin- 
ated by  a  cone  of  copper,  and  leaving  out  of  consideration  what  is 
known  as  the  preventive  action,  let  us  examine  the  phenomena  which 
are  produced  during  storms. 

"  The  copper  cone  may  still  sometimes  present  the  spectacle  of  a  lu- 
minous star,  but  less  often  than  sharp  points  of  gold  or  platinum ;  even 
then  it  resists  fusion  by  reason  of  its  form,  and,  above  all,  by  reason  of 
its  great  conducting  power.  If  the  lightning  should  strike,  it  is  by  the 
copper  cone  that  it  penetrates  the  rod,  and  it  is  by  the  rod  that  it  passes 
to  the  subterranean  water-bed  and  is  neutralized.  The  two  points  of 
departure  of  the  lightning  reside,  one  upon  the  cloud  and  the  other  upon 
the  summit  of  the  lightning-rod  ;  there  is  no  appearance  of  light  or  of 
electricity  in  any  other  part  of  the  circuit.  The  current  produced  by  the 
lightning  passes  through  the  entire  substance  of  the  conductor,  just  as 
the  current  produced  by  an  electric  or  voltaic  battery  passes  through  an 
iron  wire  of  sufficient  diameter. 


LIGHTNING-RODS. 


21 


"  These  are  the  phenomena  attending  an  ordinary 
stroke  of  lightning,  only  it  does  no  damage  to  the 
rod  or  to  the  edifice  which  the  latter  protects  ;  it  re- 
sembles the  innumerable  discharges  which,  during  a 
thunderstorm,  occur  in  the  middle  of  the  atmos- 
phere. 

'•  Figure  5  gives  a  section  of  the  copper  cylinder  at- 
tached to  a  stiff  iron  rod,  which  supports  it  above  the 
building." 

These  conclusions  we  consider  perfectly  judicious, 
and  they  show  us  the  utter  inutility  of  those  numer- 
ous points  which  we  find  sticking  up  all  over  our  best 
houses,  and  which  so  greatly  disfigure  them.  In  re- 
gard also  to  the  necessity  for  gilding  the  copper  cone, 
the  popular  notions  are  equally  at  fault.  We  have 
examined  the  subject  carefully,  by  experiment,  and 
have  found  that  a  common,  rough,  cast  iron  ball  draws 
sparks  almost  if  not  quite  as  well  as  a  copper  ball  gilt 
and  unvarnished.  Even  a  painted  metallic  ball  draws 
a  spark  without  any  appreciable  inferiority  to  a  bright 
brass  ball,  so  that,  for  ourselves,  we  do  not  see  the 
necessity  for  either  gilding  or  platinizing  the  end  of 
the  rod.  If  our  readers  desire  to  have  their  rods 
terminate  in  gilt  points  or  cones,  we  have  no  objec- 
tions to  offer,  except  on  the  score  of  expense  and  un- 
sightliness. 

The  terminations  which  we  recommend  are  these : 
The  rod  itself,  painted,  for  the  ridge  and  gables,  and 
cast-iron  caps  on  the  chimneys.  Such  caps  maybe 
made  highly  ornamental  instead  of  being  a  disfigure- 
ment, as  are  the  ordinary  points  with  which  most  houses  bristle,  while, 
at  the  same  time,  they  serve  a  most  useful  purpose  in  the  preservation 
of  the  chimneys  and  the  prevention  of  all  loosening  of  the  bricks — a  most 
disagreeable,  unsightly  and  dangerous,  though  a  most  common  occur- 
rence. All  we  have  to  say,  however,  is  that  if  you  desire  a  number  of  gilt 
points  sticking  up  all  over  your  house  there  is  no  objection  to  your 
putting  them  up.  Our  opinion  is,  that  they  do  little  or  no  good,  though 
they  certainly  do  no  harm,  further  than  to  disfigure  the  building.  Where 
the  roof  is  finished  off  with  railings,  crestings,  finials,  &c.,  no  better 
termination  than  these  can  be  desired. 

The  Best  Method  of  Attaching  Lightning- 
Rods  tO  Buildings. — It  is  a  very  prevalent  opinion  that  light- 
ning-rods should  be  carefully  insulated  from  the  buildings  to  which  they 
are  attached,  and  hence  most  rods  are  made  to  pass  through  glass  tubes 
or  insulators,  the  avowed  object  being  to  prevent  the  electricity  from 


FIG.  5. 


22  LIGHTNING-RODS. 

passing  into  the  building.  The  extreme  worthlessness  of  such  arrange- 
ments ought  to  be  obvious  to  any  person  that  ever  observed  a  flash  of 
lightning,  and  the  positively  dangerous  character  of  the  insulators  will 
be  apparent  to  every  one  that  carefully  studies  the  principles  which 
govern  conduction  and  induction.  That  a  flash  of  lightning  which  will 
pass  through  a  hundred  feet  of  air  should  be  unable  to  pass  from  the 
lightning-rod  to  any  other  object,  merely  because  an  inch  or  two  of  glass 
is  in  the  way,  is  a  proposition  too  absurd  to  find  favor  with  any  sensible 
man.  When,  moreover,  we  find  that  during  a  thunderstorm  this  in- 
sulator is  in  general  deluged  with  rain,  it  does  not  require  much  acumen 
to  see  that  the  little  efficiency  that  it  ever  had  will,  under  such  circum- 
stances, be  totally  destroyed.  We  may,  therefore,  set  it  down  as  toler- 
ably certain  that  none  of  the  insulators  in  ordinary  use  answer  the 
purpose  for  which  they  are  intended;  or,  in  other  words,  that  no  insula- 
tor can  be  invented  which  will  prevent  the  lightning  from  leaving  the 
rod  if  there  is  any  inducement  for  it  to  do  so.  The  latter  statement 
will  not  appear  extravagant  when  we  remember  that  the  discharge  from 
a  powerful  Rhumkorf  coil  will  pierce  through  five  inches  of  solid  glass, 
so  that,  if  a  lightning-rod  were  entirely  cased  in  a  glass  tube,  an  arti- 
ficial flash  of  lightning  can  be  produced  which  will  pass  through  it  as 
easily  as  a  spark  from  one  of  the  old  machines  would  pierce  a  card ! 
And  if  such  a  result  can  with  safety  be  produced  by  artificial  means,  in 
a  room  filled  with  people,  what  would  be  the  limit  to  the  effects  pro- 
duced by  natural  means  where  thousands  of  acres  of  cloud-surface  are 
engaged?  Insulators  do  very  well  to  talk  about,  but  as  a  security 
against  Heaven's  artillery  they  are  powerless. 

But  not  only  are  insulators  worthless — they  are  positively  dangerous, 
if  the  principle  upon  which  they  are  adopted  is  fully  carried  out,  which, 
however,  is  but  rarely  done.  A  very  little  consideration  will  show  this. 
Thus  if  a  house  be  furnished  with  a  carefully  insulated  lightning-rod, 
and  should  also  have  any  large  surface  of  metal,  such  as  a  tin  roof,  an 
extensive  system  of  gutters,  or  such  like,  connected  with  it,  it  is  easy  to 
see  that  the  house  must  resemble  a  large  Ley  den  jar,  of  which  the  tin 
roof,  or  other  mass  of  metal,  constitutes  one  coating,  and  the  lightning- 
rod  and  the  earth  constitute  the  other,  while  the  insulators  and  the  dry 
material  of  the  house  represent  the  glass  of  the  jar.  If  both  the  outside 
and  inside  of  this  jar  (the  tin  roof  and  the  earth)  had  been  connected  to- 
gether, it  would  have  been  impossible  to  have  brought  one  coating  into  a 
condition  opposite  to  that  of  the  other.  But  the  rod  being  carefully  insul- 
ated from  the  roof,  it  is  obvious  that  the  inductive  action  of  the  cloud 
will  bring  the  roof  and  the  earth  into  opposite  conditions ;  and  if  a  man 
were  to  form  the  path  of  least  resistance  between  them,  the  discharge 
would  take  place  through  his  body,  and  he  would  probably  be  destroyed. 
It  is  obvious,  then,  in  the  first  place,  that  lightning-rods  should  be  con- 
nected with  all  large  masses  of  metal  which  may  exist  in  or  upon  the 
house,  such  as  metallic  roofs,  tin  or  iron  gutters,  or  pipes,  iron  railings, 


LIGHTNING-RODS.  23 

etc.  In  the  second  place,  the  rod  should  be  attached  to  the  house  in  the 
neatest  and  least  obtrusive  method  possible.  If  the  rod  be  flat,  it  may 
be  pierced  with  small  holes  and  tacked  directly  to  the  building ;  but  a 
better  way,  both  for  round,  square,  and  flat  rods,  is  to  employ  properly 
shaped  staples  of  stout  wire.  These  staples  may  be  driven  into  the 
studding  of  wooden  houses  or  into  the  joints  of  brick  walls,  and,  when 
properly  painted,  will  not  present  an  unsightly  appearance. 

Where  something  better  than  mere  staples  is  desired, 
the  device  shown  in  the  annexed  engraving  may  be  em- 
ployed. It  consists  of  a  strap  of  metal  of  the  same  kind 
as  that  of  which  the  rod  is  made,  bent  as  shown  in  the 
engraving,  Figure  4,  and  pierced  with  two  holes,  whereby 
it  may  be  attached  to  any  structure  by  means  of  a  couple 
of  screws  as  shown.  The  advantages  of  this  device  are, 
that  it  does  not  weaken  the  rod,  is  not  unsightly,  permits 
the  rod  to  slide  on  the  building  as  it  expands  and  con- 
tracts by  heat  and  cold,  and  permits  it  to  be  easily  ap- 
FIG.  4.  plied  or  removed  without  injury  to  the  building.  Staples, 
however,  are  nearly  as  good  and  much  cheaper. 

Termination  in  the  Ground.— Upon  the  perfection  of 

the  ground  termination  mainly  depends  the  value  of  the  lightning-rod. 
If  this  be  defective,  no  other  good  features  can  possibly  make  up  for  it. 
And  yet,  so  little  is  it  understood,  that  a  careful  examination  of  a  very 
large  number  of  rods  leads  us  to  believe  that  fully  one-half  the  light- 
ning-rods in  existence  are  defective  in  this  respect,  and,  consequently, 
furnish  but  an  insufficient  protection. 

In  discussing  the  proper  size  of  the  rod,  we  stated  that  a  rod  of  cop- 
per need  not  be  as  large  as  a  rod  of  iron,  for  the  simple  reason  that 
copper  is  a  better  conductor  than  iron.  Now,  it  is  well  known  that  the 
terms  conductors  and  non-conductors  are  only  comparative  ;  all  conduc- 
tors resist  the  passage  of  electricity  to  a  certain  degree,  and  all  non- 
conductors allow  it  to  pass,  though  with  difficulty.  Iron  conducts 
many  thousands  of  times  better  than  water,  but  water  conducts  many 
thousands  of  times  better  than  dry  earth.  And  just  as  we  are  able,  by 
increasing  its  size,  to  make  an  iron  rod  conduct  as  freely  as  a  copper 
one,  so,  by  increasing  the  volume  of  water  or  soil  employed  to  carry  off 
the  electricity,  we  can  make  it  almost  as  efficient  as  the  metallic  con- 
ductor. These  facts  lead  us  to  the  following  conclusions :  1.  The  end  of 
the  rod  ought  to  be  made  to  terminate  in  a  layer  of  soil  that  is  perma- 
nently wet;  and  2.  The  end  of  the  rod  ought  to  expose  to  this  soil  as 
large  a  surface  as  possible. 

Permanently  moist  earth  is  to  be  attained  only  at  considerable  depths, 
—say  at  the  level  of  the  water  in  the  wells  in  the  vicinity.  Unless  we 
reach  this  point,  we  can  never  be  sure  that  our  rod  does  not  terminate 
in  dry  or  but  slightly  moist  soil ;  consequently,  no  effort  should  be  spared 


24  LIGHTNING-RODS. 

in  sinking  the  rod  to  a  sufficient  depth.  This  is  most  easily  accom- 
plished at  the  time  when  the  foundations  are  laid ;  and  we  would  advise 
all  builders  to  sink  the  lightning-rod  termination  when  they  sink  the 
foundation.  A  short  portion  of  the  stem  may  be  allowed  to  rise  above 
the  ground,  and  the  conductor  may  be  arranged  and  attached  at  a  subse- 
quent period. 

In  advising  that  the  termination  of  the  rod  should  expose  as  large  an 
extent  of  surface  to  the  soil  as  possible,  we  might,  at  first  sight,  seem 
to  be  departing  from  the  principles  laid  down  when  we  discussed  the 
proper  form  of  the  rod  ;  but  the  necessity  for  exposing  a  large  surface 
of  rod  to  the  soil  to  which  the  electricity  is  to  pass  will  be  obvious  when 
we  consider  that  this  surface  is  the  measure  of  the  section  of  solid  soil 
employed  to  carry  off  the  electricity.  Surface,  in  this  part  of  the  rod,  per- 
forms a  function  very  different  from  anything  performed  by  that  part 
of  the  surface  of  the  rod  that  is  in  contact  with  the  air.  The  advice 
generally  given  is  to  bury  a  considerable  length  of  the  rod  in  coke  (not 
charcoal),  and  the  plan  is  a  very  good  one.  Whether  iron  or  copper  is 
employed,  it  will  be  well  to  sprinkle  the  coke  copiously  with  a  strong 
solution  of  washing  soda,  for  the  purpose  of  neutralizing  any  acids  that 
might  corrode  the  metals.  If  a  trench  ten  feet  long  be  sunk  to  the 
depth  of  permanent  moisture  and  filled  to  a  depth  of  twelve  inches 
with  coke,  it  will  be  ready  to  receive  the  end  of  the  rod,  and  will  furnish 
a  path  for  all  the  electricity  that  will  ever  tend  to  escape  from  tne  clouds 
to  the  earth. 

As  great  mistakes  have  been  often  committed  in  this  matter,  we  will 
point  out  a  few  of  them.  The  general  rule  being  to  let  the  rod  end  in 
water,  rods  have  been  carried  into  cement  cisterns,  and  cisterns  hollowed 
by  human  means  out  of  the  solid  rock.  In  all  such  cases  the  end  of  the 
rod  was  virtually  insulated  by  the  walls  of  the  cistern,  and  such  rods 
would  be  worthless.  It  is  a  common  practice  amongst  lightning-rod 
men  to  form  the  earth  termination  by  simply  driving  a  crow-bar  into 
the  earth,  and  inserting  the  end  of  the  rod  in  the  hole  thus  formed.  No 
reliance  can  be  placed  on  an  earth  connection  made  in  this  manner. 
The  crow-bar  may  have  been  driven  into  perfectly  dry  sand  ;  and,  in  any 
event,  the  amount  of  surface  exposed  by  the  rod,  and  the  consequent 
section  of  earth  brought  into  action,  is  altogether  too  small.  Neither 
should  rods  be  inserted  into  open  wells  of  water,  and  especially  should 
we  avoid  doing  this  in  the  case  of  wells  that  supply  drinking-water. 
If  the  rod  be  made  of  copper,  the  well  may  be  poisoned  ;  and,  in  any 
event,  the  combined  action  of  the  air  and  water  cannot  fail  to  corrode  and 
injure  the  rod. 

The  accompanying  engraving  shows  a  new  attachment  which  formed 
the  subject  of  a  recent  commendatory  report  from  the  Committee  on 
Science  and  Arts  of  the  Franklin  Institute,  and  is  called— though  precisely 
why,  it  puzzles  us  to  tell — an  Equilibrium  Disk.  The  usual  size  of  the 
disk  is  two  feet  in  diameter.  Its  weight,  including  the  seventy -two 


LIGHTNING-ROD  IS.  25 

horizontal  and  perpendicular  discharging-points,  is  about  forty  pounds- 
It  is  made  of  one  of  the  common  metals,  though  copper  is  preferred. 
Iron,  however,  being  cheapest,  is  generally  used.  Regarding  the  mode 
of  using  it,  it  is  stated  that  it  should  be  sunk  into  the  ground  deep 
enough  to  be  surrounded  by  perpetual  moisture,  rarely  less  than  six 
feet.  By  exact  adjustment,  the  rod  passes  through  its  centre,  and  is 
firmly  solidified  to  the  disk  by  copper  surrounding.  The  fact  that  this 
device  has  been  endorsed  by  a  Committee  of  the  Franklin  Institute 
gives  it  a  certain  claim  to  public  attention,  and  will  doubtless  cause  it 


FIG.  5. 

to  be  extensively  adopted ;  but  the  inventor  of  this  attachment  must 
have  very  confused  ideas  in  regard  to  the  action  of  electricity  and  its 
relation  to  points.  That  points  serve  to  discharge  electricity  into  the 
air  by  imparting  it  to  the  molecules  of  the  air,  which  are  then  repelled 
and  fly  off,  giving  place  to  others,  we  can  very  well  understand.  But, 
when  a  point  is  embedded  in  a  solid  mass  whose  particles  are  immov- 
able, we  cannot  see  how  a  point  can  act  more  efficiently  than  any  other 
surface.  In  so  far  as  this  new  attachment  presents  a  great  extent  of 
surface,  it  is  to  be  commended  ;  but  we  must  remember  that  the  same 
extent  of  surface  might  be  obtained  in  a  far  more,  efficient  form,  and  at 
a  greatly  diminished  cost.  Moreover,  while  a  single  point,  exposed  to 
the  air,  acts  in  the  manner  which  the  inventor  of  this  device  assumes 
that  his  points  will  act,  a  multiplicity  of  points  will,  as  we  have  else- 
where stated,  act  pretty  much  like  a  ball.  We  refer  to  the  device  only 
for  the  purpose  of  condemning  it. 


26  LIGHTNING  RODS. 

Hints  to  Persons  Exposed  to  Thunderstorms. 

Little  that  is  really  of  value  can  be  said  upon  this  subject.  The  old 
directions  about  avoiding  the  shelter  of  trees  are  sound ;  though  the  ad- 
vice which  goes  to  an  opposite  extreme,  and  recommends  us  to  go  to 
the  middle  of  an  open  field,  is  decidedly  bad.  A  tall  tree  will,  in  general, 
protect  a  space  of  considerable  diameter — the  accepted  rule  giving  a 
circle  whose  diameter  is  four  times  its  height ;  though,  as  elsewhere 
noted,  we  do  not  place  implicit  confidence  in  this.  Now,  it  is  a  curious 
law  of  electrical  action,  that,  if  two  bodies  combine  to  form  the  medium 
of  conduction,  one  being  a  good  conductor  and  the  other  a  poor  one, 
the  good  conductor  does  not  carry  off  att  the  charge ;  it  merely  divides 
it  with  the  poor  conductor,  which  gets  a  share  that  is  precisely  equal  to 
its  capacity.  When  a  man  stands  beside  a  tree  that  is  struck  by  light- 
ning, the  charge  divides,  and  the  man  is  apt  to  receive  such  a  proportion 
as  is  sufficient  to  kill  him.  But,  if  he  had  stood  at  a  distance  a  little 
greater  than  the  height  of  the  tree,  the  latter  would  have  attracted  the 
bolt,  which  in  that  case  would  not  have  been  divided.  When  standing 
in  the  middle  of  an  open  field,  there  is  nothing  to  attract,  the  lightning 
from  us,  and  we  run  great  risk  of  being  struck. 

The  old  directions  about  feather  beds,  glass  windows,  etc.,  are  all 
nonsense.  One  of  the  safest  of  all  places  is  a  house  well  protected  by 
good  lightning-rods  ;  one  of  the  most  dangerous  is  a  barn  filled  with 
new  hay  and  without  a  rod.  In  a  house  unfurnished  with  lightning- 
rods,  the  most  dangerous  places  are  near  the  fireplace  or  chimney,  or 
near  those  corners  down  which  the  water-spouts  descend.  Referring  to 
our  remarks  about  the  division  of  a  lightning-stroke  when  two  parallel 
paths  are  presented  to  it,  it  must  be  noted  that  the  quantity  of  the 
charge  that  passes  down  each  conductor  will  be  in  proportion  to  its 
conducting  power.  A  good  lightning-rod  has  a  power  of  conduction  so 
much  in  excess  of  the  body  of  a  man,  that  there  would  be  very  little 
left  to  pass  through  him.  On  the  other  hand,  the  conducting  power  of 
trees,  the  soot  of  chimneys,  tin  water-pipes,  bell-wires,  etc.,  is  so  low, 
that  a  human  body  might  have  assigned  to  it  a  greater  proportion  of 
the  charge  than  it  could  bear.  A  few  years  ago  some  wise-acre  invent- 
ed a  portable  lightning-rod  consisting  of  an  umbrella  having  a  metal 
stem,  to  the  lower  part  of  which  was  attached  a  chain  that  was  allowed 
to  drag  along  the  ground.  Such  a  contrivance  is  not  only  useless,  but 
dangerous.  It  would  be  utterly  impossible  to  give  such  a  portable  rod 
a  good  ground  connection ;  and  without  this  a  lightning-rod  is  worse 
than  useless. 

The  carrying  of  metal  rods  or  bars  is,  of  course,  dangerous,  because 
every  mass  of  metal  tends  to  open  up  a  line  of  least  resistance  of  which 
it  will  form  a  part ;  though  metal  cannot  be  said  to  attract  lightning  in 
the  sense  that  a  magnet  attracts  a  bar  of  iron. 

It  has  been  said  that  a  lightning-rod  no  more  attracts  the  lightning 
than  a  water-spout  on  a  house  attracts  the  rain.  This  is  but  partially 


LIGHTNING-RODS.  27 

true.    The  rod  attracts  the  lightning  to  about  the  same  extent  that  an 
open  sluice  may  be  said  to  attract  the  escaping  waters  of  a  pond. 

Lightning-Rod  Swindles,— Next  to  the  substitution  of 
saw-dust  packages  for  counterfeit  money,  and  the  sale  of  brass  jewelry, 
the  business  of  putting  up  lightning-rods  is  a  favorite  field  for  the  op- 
erations of  the  swindling  fraternity.  Indeed,  to  such  an  extent  is  it 
carried,  that  at  the  West  there  are  large  companies  formed  whose  gains 
are  derived  chiefly  from  the  swindling  part  of  their  schemes,  and  not 
from  the  legitimate  business  of  honestly  putting  up  good  rods.  These 
scoundrels  operate  in  a  manner  somewhat  like  this :  Approaching  a 
house  in  the  absence  of  the  men,  they  so  terrify  the  ladies  by  means  of 
horrible  stories  of  persons  killed  and  houses  destroyed  by  lightning  that 
when  the  proprietor  returns  he  gets  no  peace  until  a  rod  is  ordered. 
Then  these  fellows  get  an  order  for  a  rod  at  so  much  per  foot,  they 
giving  a  verbal  estimate  of  the  amount  required,  which  estimate  is  not 
embodied  in  the  contract,  and  forms  no  part  thereof.  They  then  go  to 
work  ;  and  being,  by  the  terms  of  the  contract,  the  sole  judges  of  the 
amount  required,  they  contrive  to  put  on  three  or  four  times  the  num- 
ber of  feet  originally  mentioned.  Of  course,  when  the  bill  is  presented, 
the  victim  sees  no  way  of  escape  from  the  terms  of  his  written  contract, 
and  he  pays  the  amount ;  and,  when  we  remember  that  for  a  rod  which 
costs  them  ten  cents  per  foot,  these  fellows  frequently  charge  50  or  70 
cents,  it  will  be  readily  seen  that  the  transaction  is  a  profitable  one  for 
them.  There  is  no  doubt  but  that  many  of  these  suits  might  be  suc- 
cessfully resisted,  though  of  course  the  best  way  is  to  avoid  falling  into 
the  trap ;  and,  to  enable  our  readers  to  escape  it,  we  offer  the  following 
hints : 

If  you  make  a  bargain  with  a  professional  lightning-rod  man  to  put 
up  a  rod  for  you,  see  that  the  contract  specifies  the  number  of  feet  as 
well  as  the  price  per  foot.  In  your  selection  of  the  kind  of  rod,  you 
will  probably  be  guided  by  what  we  have  previously  said  on  this  sub- 
ject. If  so,  then  remember  that  the  best  copper  rod  need  not  cost,  for 
materials  alone,  over  fifteen  to  twenty  cents  per  foot ;  and,  if  you 
have  read  attentively  our  paragraph  on  the  arrangement  of  the  rod, 
you  will  find  no  difficulty  in  determining  where  it  should  be  carried, 
and,  consequently,  the  number  of  feet  that  will  be  required. 

The  point  in  which  you  will  be  most  apt  to  be  cheated  will  be  the 
ground  connection.  We  have  already  given  abundant  directions  in  re- 
gard to  this  matter.  Your  only  chance  for  safety  lies  in  giving  this 
part  of  the  work  your  personal  supervision  during  its  progress ;  after  it 
is  finished,  no  man  can  tell  whether  or  not  it  is  efficient,  without  such 
an  examination  as  would  cost  as  much  as  it  would  to  do  the  work 
over  again. 

Surveying  Lightning-Rods  for  Insurance  Pur- 
poses.— Insurance  companies  cannot,  with  safety,  ignore  the  value 


28  LIGHTNING-RODS, 

of  the  lightning-rod.  We  therefore  give  a  few  hints,  which  may  prove 
of  value  to  insurance  agents  who  wish  to  determine  whether  a  house 
or  barn  is  efficiently  protected. 

The  general  principles  governing  the  subject  have  been  already  dis- 
cussed ;  but  it  must  be  borne  in  mind  that  a  rod  may  be  efficient,  and  yet 
neither  economical  nor  neat.  Moreover,  while,  for  purposes  of  fire  insu- 
rance, insulators  are  of  no  benefit,  they  are  not  a  source  of  danger  as 
they  unquestionably  are  in  regard  to  life.  Points,  etc.,  are  not  of  much 
consequence  if  the  rod  has  been  properly  arranged ;  in  regard  to  this 
we  would  refer  to  the  paragraph  on  tnat  subject.  So  far  as  that  por- 
tion of  the  rod  that  is  above  ground  is  concerned,  the  chief  conditions 
to  be  observed  are,  that  it  shall  be  large  enough,  that  it  shall  be  contin- 
uous, and  that  it  shall  be  well  arranged.  It  is  in  regard  to  the  ground 
connection  that  the  great  difficulty  arises.  To  examine  a  ground  con- 
nection would  be  a  work  of  great  labor  and  expense  ;  and  therefore  we 
must  rely  upon  other  sources  of  information.  We  see  no  safe  mode  of 
obtaining  the  required  information  except  by  the  written  affidavit  of 
the  parties  concerned.  We  lay  great  stress  upon  the  importance  of 
obtaining  a  written  affidavit ;  mere  verbal  communications,  and  state- 
ments made  in  writing  without  the  solemnity  of  an  affidavit,  are  in 
general  too  vague  to  be  depended  upon. 

The  points  of  inquiry  should  be  in  regard  to  the  depth  to  which  the 
rod  is  carried,  the  mode  in  which  it  is  arranged,  and  the  extent  of  sur- 
face that  it  presents  to  the  soil.  After  these  points  have  been  testified 
to,  the  surveyor  should  determine,  by  examining  the  wells  in  the 
vicinity,  and  by  other  indications,  the  probable  depth  at  which  per- 
manent moisture  is  to  be  found ;  and  from  these  data  the  efficiency  of 
the  ground  connection  can  be  determined.  Any  falsification  in  the 
statement  made  by  the  insured  ought  to  void  the  policy ;  and.  if  an  ac- 
cident should  occur  from  lightning,  no  time  ought  to  be  lost  in  making 
a  thorough  examination. 


APPENDIX. 


HOME-MADE    LIGHTNING-RODS. 

Since  the  issue  of  this  little  volume,  we  have  received  numerous 
inquiries  in  regard  to  the  best  material,  etc.,  for  the  construction  of 
Lightning-Rods,  by  those  who  do  not  make  a  regular  business  of  put- 
ting them  up.  It  frequently  happens  that  farmers,  builders,  carpenters* 
and  mechanics  in  general,  have  occasion  to  put  up  Lightning-Rods, 
and  find  a  difficulty  in  procuring  the  necessary  material  and  fixtures 
for  the  purpose.  To  such  persons  the  following  hints  may  prove 
useful. 

In  very  out-of-the-way  places,  the  rod  may  be  made  of  round  or 
square  iron  rod,  five  eighths  of  an  inch  in  diameter.  The  lengths  may 
be  welded  together  in  a  blacksmith's  shop,  and  drawn  to  the  building 
for  which  it  is  intended.  A  single  rod,  leading  by  the  shortest  path 
from  the  highest  chimney  to  the  ground,  is  all  that  need  be  made  in 
one  piece.  Those  parts  of  the  rod  that  lie  along  the  ridge  and  the  gable, 
may  be  connected  to  the  main  rod  simply  by  a  hook, — which  should, 
however,  be  closed  as  tightly  as  possible  upon  the  rod  which  it  clasps ; 
and  if  such  joints  occur  over  straw,  shingles,  or  boards,  it  will  be  well 
to  slip  a  piece  of  sheet-iron,  tin,  or  zinc,  under  the  joint,  and  secure  it 
in  its  place  by  a  few  tacks. ,  No  fear  need  be  entertained  that  the  elec- 
tricity will  not  follow  the  rod  across  such  joints.  The  electricity  pro- 
duced by  rubbing  a  common  glass  bottle  with  a  piece  of  flannel  will 
jump  across  a  break  half  an  inch  wide;  and  it  is  therefore  ridiculous 
to  suppose  that  a  break  of  a  hundredth  of  an  inch  would  impede  the 
progress  of  a  thunderbolt.  But  wherever  such  a  break  exists,  a  spark 
may  be  produced,  and  it  is  to  prevent  the  possibility  of  such  a  spark 
setting  fire  to  light  combustibles  that  we  recommend  the  use  of  thin 
sheet-metal  laid  under  the  joint. 

But  where  good  copper  wire  can  be  readily  procured,  it  forms  very 
much  better  material  for  the  construction  of  home-made  Lightning- 
Rods.  The  most  suitable  size  is  No.  0  or  00,  which  gives  a  solid  section 
that  is  several  times  that  of  the  tubular  copper-rods  in  common  use, 
most  of  which,  by  the  way,  are  so  light  that  they  can  not  afford  efficient 
protection  against  a  heavy  stroke.  But  notwithstanding  the  increased 
weight  and  efficiency  of  the  plain  wire,  it  will  be  found  to  cost  much 
less  per  foot  than  the  fancy  rods  usually  sold  by  itinerant  venders. 
Such  wire  can  be  obtained  of  an}7  respectable  hardware  merchant,  or 
it  may  be  procured  direct  from  the  manufacturers,  of  whom  there 


30  APPENDIX. 

are  several, — amongst  others  the  Waterbury  Brass  Company,  whose 
agency  is  at  52  Beekman  Street,  New  York.  The  wire  comes  in  rolls 
measuring  thirty  to  lorty  feet  in  length.  The  following  gives  the 
diameters  and  weights  per  hundred  feet  of  the  sizes  suitable  for  Light- 
ning-Rods: — 

Number  on  Weight  of 

wire-guage.  Diameter.  100  feet. 

000        .  .  .409  inches.     .        .        50  Ibs. 

00        .  .  .364      "  40     " 

0  .  .  .324      "  32     " 

1  .  .  .289      "  .        .        25£  " 

2  .  .  .257      "  20     " 

Joints  are  easily  made  by  flattening  the  ends  of  the  pieces  to  be 
united,  binding  them  together  with  fine  copper  wire,  and  soldering  the 
whole,  binding-wire  and  all,  into  a  solid  mass,— a  very  simple  and  easy 
job.  For  attaching  such  a  rod  to  a  house,  nothing  is  better  than  small 
wire  staples.  A  flat  strip  may  be  made  to  look  much  better  than  a 
wire,  but  is  not  in  any  respect  more  efficient. 

From  the  fact  that  it  is  much  more  pliable  than  copper  wire,  and 
can  be  obtained  in  pieces  of  almost  any  length,  the  copper  wire-rope 
that  is  now  so  extensively  used  for  many  purposes,  is  an  excellent 
material  for  lightning-rods .  It  can  be  put  up  with  less  trouble  than 
any  other  kind  of  material,  and  it  is  the  most  convenient  for  forming 
a  ground  connection;  for,  by  untwisting  the  ends  for  a  length  of  sev- 
eral feet,  it  is  easy  to  spread  the  rope  over  a  large  surface  of  earth. 

Rods  carefully  constructed  of  any  of  these  materials  will  prove 
far  superior  to  those  in  common  use,  besides  being  far  cheaper.  Of 
course  all  the  precautions  detailed  in  the  body  of  this  work  in  regard 
to  arrangement,  ground  connection,  etc.,  must  be  fully  carried  out,  if 
we  would  secure  perfect  protection.  In  general,  most  of  the  details 
are  sufficiently  well  attended  to,  with  the  exception  of  the  ground 
connection.  At  this  point,  almost  all  the  lightning-rods  ordinarily 
put  up,  fail.  In  our  first  edition  we  dwelt  upon  this  point  very  fully, 
and  further  observation  not  only  fully  confirms  the  remarks  made  on 
page  23,  but  leads  us  to  believe  that  our  statements  were  not  half 
strong  enough.  Mr.  Brooks,  the  well-known  inventor  of  the  Paraffin 
Insulator,  a  man  whose  practical  acquaintance  with  the  science  of 
electricity  is  perhaps  as  extensive  as  that  of  any  man  in  the  country, 
writes  me  as  follows:  "  There  were  three  disasters  in  this  city  (Phila- 
delphia) last  season,  involving  a  loss  of  over  two  hundred  and  fifty 
thousand  dollars,  by  lightning— Solm's  Woollen  Factory,  Morris  Iron 
Foundry,  and  the  Point  Breeze  Refining  Co.,  every  one  of  which  had 
a  lightning-rod;  and  the  cases  of  general  interest  in  the  country  are 
of  such  common  occurrence  that  I  have,  as  a  matter  of  interest,  meas- 
ured the  resistance  of  these  joints  to  earth,  and  find  the  average  to  be 
above  the  resistance  of  a  hundred  miles  of  telegraph-wire."  That  is 
to  say,  a  flash  of  lightning  would  rather  travel  one  hundred  miles 
along  a  telegraph-wire  than  pass  from  these  lightning-rods  to  the 
ground  !  Can  we  wonder  that  buildings  furnished  with  lightning-rods 
are  so  often  injured  when  struck? 


APPEMMX,  ;:"•>• I ''.  I *•  i  i />%     31 

Mr.  Brooks  advises  that  in  cities  the  lightning-rods  should  be  con- 
nected with  the  gas  or  water  pipes.  So  far  as  the  latter  are  concerned, 
there  can  not  be  much  objection,  but  in  regard  to  a  connection  with 
the  gas-pipes,  we  hold  different  views.  We  must  remember  that  there 
are  two  sides  to  this  question,  and  two  parties  to  be  consulted, — the 
owner  of  the  lightning-rod  and  the  gas  company.  Looking  wholly  to 
the  interest  of  the  former,  we  would  advise  him  by  all  means  to  con- 
nect his  rod  to  the  gas  or  water  pipes,  or  both,  but  to  be  sure  that  the 
connection  is  made  outside  of  his  own  premises,  as  instances  have 
occurred  where  the  pipes  connected  with  the  metre  have  been  dislo- 
cated, and  the  gas  set  on  fire  by  a  lightning  stroke.  If,  however,  the 
rod  be  carefully  connected  with  the  pipes  outside  of  the  house,  no 
danger  can  accrue  to  the  house  from  this  source.  But  how  is  it  with 
the  pipes  themselves  ?  Those  who  are  familiar  with  the  character  of 
our  streets,  at  the  depth  at  which  ordinary  gas-pipes  are  laid,  know- 
that  the  soil  is  generally  about  as  dry  as  soil  can  be,  and  it  is  kept  in 
this  condition  by  the  pavement  above,  which  shields  it  from  the  rain, 
and  by  the  drains  below,  which  carry  oft'  any  little  moisture  that  may 
find  its  way  below  the  surface.  These  pipes,  therefore,  are  embedded 
in  an  almost  perfect  non-conductor,  and  any  electricity  that  enters 
them  must  flow  along  to  a  considerable  distance  before  it  can  find  an 
efficient  outlet.  In  the  mean  time,  it  meets  with  an  obstacle  at  every 
joint,  for  these  joints  are  always  made  in  such  a  way  as  to  be  virtually 
non-conductors.  At  each  joint  of  the  pipes,  therefore,  an  electric  ex- 
plosion will  occur;  and,  if  the  electricity  be  in  sufficient  quantity,  the 
joint  may  be  entirely  ruptured,  and  instances  are  on  record  where  gas- 
pipes  have  been  disjointed,  and  the  gas  allowed  to  escape.  While, 
therefore,  a  connection  with  the  gas-mains  must  prove  very  advan- 
tageous to  the  individual  whose  house  is  to  be  protected,  it  may  prove 
very  disastrous  to  the  public  at  large.  We  hold,  therefore,  that  no 
man  has  a  right  to  connect  his  lightning-rod  with  the  gas-pipes  of  our 
cities.  Let  each  one  find  a  ground  connection  for  himself,  unless  in- 
deed two  or  more  neighboring  householders  should  decide  to  combine 
for  the  formation  of  a  thoroughly  efficient  ground  termination.  Where 
four  parties  combine  for  this  purpose,  the  advantages  would  be  quad- 
rupled, and,  at  the  same  time,  there  are  fortunately  no  counterbalancing 
disadvantages. 

In  the  instructions  issued  by  the  Inspector-General  of  Fortifications, 
British  army,  which  instructions  have  been  adopted  in  the  Ordnance 
Manual  published  by  the  authority  of  the  United  States  Government, 
and  are  substantially  the  same  as  those  contained  in  our  own  little 
work,  the  following  passage  occurs:  "  If  it  be  possible,  in  regulating 
the  surface-drainage,  to  lead  a  flow  of  water,  during  the  rain  which 
generally  accompanies  thunder-storms,  over  the  sites  of  the  trenches 
in  which  the  ground  terminations  are  laid,  it  will  be  an  additional 
precaution."  The  advice  deserves  attention. 


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HOW   TO   USE   THE  MICROSCOPE. 

A  Simple  and  Practical  Book,  intended  for  beginners. 
BY  JOHN  PHIN, 

Editor  of  "  The  American  Journal  of  Microscopy." 

Second  Edition.    Greatly  Enlarged,  with  50  illustrations  in  the  text, 

and  4  full-page  engravings  printed  on  heavy  tint  paper. 


WHAT  A  MICROSCOPE  is  —  Different  Kinds  of  Microscopes.  —  Simple  Mi- 
croscopes.— Hand  Magnifiers.  —  The  Coddington  Lens.  —  The  Stanhope 
Lens.  —  Easpail's  Microscope  __  -The  Excelsior  Microscope.  —  Twenty-five 
cent  Microscopes  aud  how  to  make  them.  —  Penny  Microscopes. 

COMPOUND  MICROSCOPES.—  Different  kinds  of  Objectives  __  Non-A.chrom« 
a*ic  Objectives.—  French  Achromatic  Objectives—  Objectives  of  the  English 
Form.  —  Immersion  Objectives  —  Focal  Lengths  corresponding  to  the  num- 
bers employed  by  Nachet,  Hartnack  and  Guudlach. 

How  TO  CHOOSE  A  MICROSCOPE.—  Microscopes  for  Special  Purposes.— 
Magnifying  Power  required  for  different  purposes.  —  How  to  judge  of  the 
quality  of  the  different  parts  of  the  Microscope. 

ACCESSORY  APPARATUS.  —  Stage  Forceps,  Animalcule  Cage,  etc. 

ILLUMINATION.  —  Sun  Light.  —  Artificial  Light.  —  Bulls-Eye  Condenser.— 
Side  Reflector.—  The  Lieberkuhn.—  Axial  Light.—  Oblique  Light.—  Direct 
Light.  3 

How  TO  USE  THE  MICROSCOPE.—  How  to  Care  for  the  Microscope. 

How  TO  COLLECT  OBJECTS.  —  Where  to  find  Objects.  —  What  to  Look  for.  — 
How  to  Capture  Them.—  Nets.—  Bottle-Holders.  —  Spoons.—  New  Form  of 
Collecting  Bottle.—  Aquaria  for  Microscopic  Objects.—  Dipping  Tubes. 

THE  PREPARATION  AND  EXAMINATION  OF  OBJECTS.  —  Cutting  Thin  Sections 
of  Soft  Substances.  —  Sections  of  Wood  and  Bone.  —  Improved  Section  Cut- 
ter.— Sections  of  Bock.—  Knives.—  Scissors.—  Needles.—  Dissecting  Pans 
and  Dishes.  —  Dissecting  Mici^scopes.  —  Separation  of  Deposits  from 
Liquids.  —  Preparing  whole  Insect.3.  —  Feet,  Eyes,  Tongues,  \Yings,  etc.,  of 
Insects.  —  Use  of  Chemical  Tests.  —  Liquids  for  Moistening  Objects.  —  Re- 
fractive Power  of  Liquids.—  Covers  for  Keeping  out  Dust.—  Errors  in  Micro- 
scopical Observations.  > 

PRESERVATION  OF  OBJECTS.—  General  Principles.—  Recipes  for  Preserv- 
ative Fluids.  —  General  Rules  for  Applying  them. 

MOUNTING  OBJECTS.—  Apparatus  aud  Materials  for:  Slides,  Covers,  Cell«, 
Turn-Table,  Cards  for  Making  Cells,  Hot-Plate,  Lamps,  Retort  Stand, 
Slide-Holder,  Mounting  Needles,  Cover  Forceps,  Simple  Form  of  Spring 
Clip,  Centering  Cards,  Gold  Size,  Black  Japan,  Brunswick  Black,  Shellac, 
Bell's  Cement,  Sealing  Wax  Varnish,  Colored  Shellac,  Damar  Cement,  Mar- 
ine Glue,  Liquid  Glue,  Dextrine.  —  Mounting  Transparent  Objects  Dry.  — 
Mounting  in  Balsam.  —  Mounting  in  Liquids.  —  Mounting  of  Whole  In- 
sects.— How  to  Get  Rid  of  Air-Bubbles  —  Mounting  Opaque  Objects. 

FINISHING  THE  SLIDES. 

Hay  be  obtained  from  any  Bookseller  or  News  Agent,  or  will  be  sent  by 
mail,  postage  paid,  on  receipt  of  price. 


THE  AMERICAN 

JOURNAL    OF     MICROSCOPY, 

-A.3STZD 

POPULAR    SCIENCE. 


PROSPECTUS. 

The  object  of  the  JOTJRXAL  OF  MICROSCOPY  ia  to  diffuse  a  knowledge  of  the 
best  methods  of  using  the  Microscope;  of  all  valuable  improvements  in  the  in- 
strument and  its  accessories;  of  all  new  methods  of  microscopical  investigation, 
aud  of  the  most  recent  results  of  microscopical  research.  The  JOURNAL  does 
not  address  itself  to  those  who  have  long  pursuer!  certain  special  lines  of  re- 
search, and  whose  wants  can  be  supplied  only  by  elaborate  papers,  which,  from 
their  thoroughness,  are  entitled  to  be  called  monographs  rather  than  mere  arti- 
cles. It  is  intended  rather  to  meet  the  wants  of  those  who  use  the  microscope 
for  purposes  of  general  study,  medical  work,  class  insructiou,  a;  d  even  amuse- 
ment, aud  who  desire,  in  addition  to  the  information  afforded  by  text-books, 
such  a  knowledge  of  what  others  are  doing  as  can  be  derived  only  from  a  peri- 
odical. With  this  object  in  view,  therefore,  the  publishers  propose  to  make  the 
JOUBNAL  BO  simple,  practical  and  trustworthy,  that  it  will  prove  to  the  advantage 
of  every  one  who  uses  the  microscope  at  all  to  take  it. 

ILLUSTRATIONS  —  The  JOURNAL  will  bo  freely  illustrated  by  engravings 
representing  either  objects  of  natural  history  or  apparatus  connected  with  the 
microscope. 

TRANSACTIONS  OF  SOCIETIES.—  THE  AMERICAN  JOURNAL  OF  MICROSCOPY 
is  not  the  organ  of  any  Society,  but  it  gives  the  proceedings  of  all  Societies 
whose  officers  send  us  a  report.  As  the  JOURNAL  is  devoted  wholly  to  Micro- 
scopy, and  is  in  good  form  aud  size  for  binding,  no  better  medium  can  be  had 
for  preserving  the  scientific  records  of  any  society.  Matters  of  mere  business 
routine  we  are  frequently  obliged  to  omit  for  want  of  room. 

EXCHANGES.  —  An  important  feature  of  the  JOURNAL  is  the  exchange  column, 
by  means  of  which  workers  in  different  parts  of  the  country  are  enabled,  with- 
out expense,  except  for  postage,  to  exchange  slides  and  materials  with  each  other. 


During  the  first  two  years  of  its  existence,  the  subscription  to  the  AMERICAN 
JOURNAL  OF  MICROSCOPY  was  only  fifty  cents  per  year,  but  at  the  request  of 
more  than  two-thirds  ol  the  subscribers,  the  size  of  the  JOURNAL  has  been 
doubled,  and  the  price  raised  to 

OXE    DOLLAR    PER    YEAR. 

Four  copies  for  three  dollars.  Those  who  wish  to  economize  in  the  direction 
of  periodicals,  would  do  well  to  examine  our  clubbing  list. 

FOREIGN  SUBSCRIBERS.—  The  JOURNAL  will  be  sent,  postage  paid,  to  any 
country  in  the  Postal  Union  for  $1.24,  or  6  shillings  sterling  per  year.  English 
postage  stamps,  American  currency  or  American  postage  stamps  taken  in  pay- 
ment. In  return  for  a  postal  order  or  draft  for  £1  5s.,  five  copies  of  the  JOURNAL 
will  be  furnished  and  mailed  to  different  addresses.  Make  all  drafts  and  postal 
orders  payable  to  John  Phin. 

BACK  VOLUMES.—  We  have  on  hand  a  few  copies  of  Vols.  I  and  II,  bound  in 
ha  dsome  cloth  cases,  which  we  offer  for  $1  25  each.  Vols.  I  and  II,  bound,  and 
the  numbers  of  Vol.  Ill,  as  issued,  we  offer  for  $2.50.  We  can  no  longer  supp  y 
complete  sets  of  1876-7  in  sheets.  To  those  who  wish  to  examine  the  journal,  we 
will  send  ten  odd  numbeis  for  25  cents. 


The  JOURNAL  or  MICROSCOPY,  from  its  very  nature,  is  a  visitor  to  the  very 
best  families,  and  its  value  as  an  advertising  medium  has  therefore  proved  to  be 
much  above  that  of  average  periodicals.  A  few  select  advertisements  will  be 
inserted  at  the  rate  of  30  cents  per  line,  nonpariel  measure,  of  which  twelve 
lines  make  au  inch.  Addi  ess 

AMERICAN  JOURNAL  OF  MICROSCOPY, 

P.  O.  Box  2852,  New  York. 


NEW  BOOKS  IN  PRESS, 


Supplements  to  this  Catalogue  will  be  issued  from  time  to 
time,  and  will  be  sent  free  to  any  one  desiring  them.  Since 
our  removal  to  the  larger  and  more  commodious  premises  at 
14  Dey  Street,  we  have  made  arrangements  to  greatly  extend 
our  publishing  business. 

The  following  books  are  in  a  forward  state  of  preparation, 
and  will  be  issued  at  an  early  day : 

The  Aquarium. 

A  Practical  Treatise.  With  nearly  one  hundred  illus- 
trations. By.  A.  W.  Boberts,  formerly  of  Barnum's 
Museum  Aquaria,  Collector  for  the  New  York  Aquarium, 
and  Superintendent  of  Sea  Side  Aquarium.  „, 

Mr.  Roberts  having  had  over  thirty  years  experience,  has  therefore 
been  able  to  produce  a  thoroughly  practical  book.  The  accuracy  of 
the  illustrations  are  guaranteed,  by  the  fact  that  they  are  carefully 
drawn  and  engraved  by  the  author  from  life. 

Taxidermy;  or,  The  Art  of  Preserving  and  Stuffing  Beasts, 
Birds  and  Fishes. 

This  work  is  by  a  practical  Taxidermist,  who  is  perhaps 
better  known  than  any  other  of  the  profession  in  this 
country.  It  will  be  simple,  thorough  and  practical. 

Fret  and  Scroll  Saws:  Their  Construction  and  Use. 

'  Notwithstanding  the  many  works  on  this  subject  now  before  the 
public,  we  think  that  there  is  room  for  one  more.  The  volume  which 
we  propose  to  bring  out  is  by  a  gentleman  whose  profession  (that  of 
an  architect)  has  given  him  special  qualifications  for  producing  a 
really  good  book,  and  one  free  from  the  errors  of  taste  and  instruc- 
tion in  practical  workmanship,  which  have  disfigured  so  many  at- 
tempts in  this  direction.  It  will  be  very  copiously  illustrated. 

We  shall  also  issue  a  portfolio  of  twelve  designs,  full  working  size, 
for  Fret  and  Scroll  Saw  Work.  The  set  will  be  sold  at  a  very  moder- 
ate price. 


Young  Scientist  Companion. 

This  is  a  small  pocket  book  intended  for  the  practical 
man,  as  well  as  the  young  scientist.  It  will  contain 
rules  and  data  for  calculations ;  tables  of  physical  and 
chemical  data ;  recipes ;  processes,  and  in  fact  just  that 
practical  information  which  every  man  has  so  often  oc- 
casion to  refer  to. 


Cage  Birds,  and  How  to  Care  for  Them. 

With  a  full  account  of  the  best  methods  of  training,  etc. 
This  work  is  by  a  lady  who  has  long  been  known  as  a  successful 
authoress,  and  who  is  noted  for  her  skill  in  the  care  of  household  pets- 
It  will  be  splendidly  illustrated  with  nearly  one  hundred  engravings, 
and  cannot  fail  to  find  its  way  into  every  home  where  a  canary  or 
other  song  bird  is  kept. 

Manual  of  Urinary  Examination,.  Chemical  and  Microscopical. 

For  the  Use  of  Physicians,  Medical  Students  and  Clinical 
Assistants.  By  Frank  M.  Deems,  M.  D.,  Laboratory  In- 
structor in  the  University  Medical  College,  New  York ; 
Member  of  the  Medical  Society  of  the  County  of  New 
York ;  Member  of  the  New  York  Microscopical  Society 
etc.,  etc. 

How  to  Learn  to  Draw. 

By  an  old  Teacher  of  Drawing. 

This  is  the  first  of  a  series  of  small  practical  books  to  be  called 
"  The  Young  Scientist  Manuals."  It  does  not  profess  to  teach  the 
science  or  art  of  Drawing;  it  is  intended  rather  to  point  out  to  the 
beginner  the  best  methods  of  going  to  work.  It  is  intended  for  self- 
taught  students,  and  contains  a  great  deal  that  is  not  to  be  found  in 
the  books,  but  is  generally  imparted  to  the  pupil  directly  by  the 
teacher. 

The  price  of  this  series  has  been  fixed  at  20  cents  each,  neatly  and 
strongly  bound  in  boards. 


CATALOGUE  OF  MICHOSCOPES.-We  are  preparing  a  CATA- 
LOGUE OF  MICEOSCOPES,  with  hints  in  regard  to  the  selection  of  a 
microscope,  especially  as  regards  its  suitability  for  the  various  purposes 
for  which  microscopes  are  used.  A  copy  of  this  catalogue  will'-  be  sent 
free  to  any  one  applying  for  it.  Applications  received  before  the 
Catalogue  is  published  will  be  carefully  registered,  and  filled  as  soon  as 
possible. 


SEW  WORKING  MICROSCOPE, 

Manufactured  by  Geo.  Wale. 

Price— With  two  Eye-Pieces,  2-3  and  1-5  Objectives,  Iris 

Diaphragm,  and  Black  Walnut  Case,          -          -          -    $35. 

INDUSTRIAL  PUBLICATION  COMPANY, 

14  Dey  Street,  New  York,  Sole  Agents. 


THE  NEW  WORKING   MICROSCOPE, 

This  Microscope  has  just  been  brought  out  by  Mr.  Geo.  Wale,  whose 
reputation  as  a  maker  of  fine  stands  is  so  well  known.  It  embodies 
several  new  and  important  features,  foremost  amongt  which  is  the 
method  of  hanging  the  body,  so  that  it  may  be  made  to  incline  at 
any  angle.  The  method  now  in  general  use  for  this  purpose  changes 
the  position  of  the  centre  of  gravity  of  the  instrument,  and  renders 
the  microscope  more  or  less  unsteady.  The  new  method  avoids  this 
difficulty,  and  at  the  same  time  furnishes  a  secure  and  convenient 
means  of  clamping  the  body  at  any  position— a  point  of  considerable 
importance,  when  the  instrument  is  used  for  some  purposes. 

The  stage  is  of  a  new  construction,  very  thin,  so  as  to  admit  the 
greatest  obliquity  in  the  illumination  of  objects,  and  with  clips  which 
move  round  it,  thus  giving  many  of  the  advantages  of  a  rotary  stage. 
The  clips  may  be  easily  and  quickly  removed,  so  as  to  leave  a  clear 
stage,  and  they  may  also  be  so  applied  as  to  hold  the  slide  against  the 
under  side  of  the  stage,  when  very  oblique  light  is  required  for  re- 
solving difficult  test  objects. 

There  are  two  means  of  adjusting  for  focus,  a  coarse  movement  by 
means  of  a  well-made  rack  and  pinion,  and  a  fine  movement,  in.  which 
the  entire  body  is  moved  by  what  is  generally  called  a  "micrometer'' 
screw,  acting  on  a  lever.  The  latter  movement  has  this  great  advan- 
tage, that  it  does  not  change  the  distance  between  the  eye-piece  and  the 
objective  (as  is  the  case  with  most  of  the  English  fine  movements),  and 
consequently  does  not  vary 'the  magnifying  power  of  the  instrument— 
an  important  point  in  making  delicate  micrometric  measurements. 

The  diaphragm  is  of  the  Iris  pattern,  a  form  which  is  generally 
acknowledged  to  be  the  best,  but  which  has  hitherto  been  very  costly, 
those  usually  supplied  being  sold  for  $16.  This  Iris  diaphragm  is  a  new 
form,  which,  with  several  other  features  of  this  stand,  has  been  patented 
by  Mr.  "Wale.  It  may  be  easily  and  quickly  applied  or  removed. 

The  New  Working  Microscope  is  of  substantial  make,  elegant  design, 
and  thoroughly  good  workmanship.  It  has  the  Society  screw;  draw- 
tube,  with  Society  screw  at  lower  end  for  receiving  long  focus  objectives, 
analyzing  prism,  etc.;  plane  and  concave  mirrors,  the  distance  of 
which  from  the  object  may  be  varied ;  two  Eye-pieces ;  2-3  and  1-5 
Objectives  of  .Wale's  Histological  Series.  The  1-5  easily  and  clearly 
resolves  the  P.  Angulatumytitln  light  of  a  very  slight  degree  of  obliquity. 

This  Microscope,  with  draw-tube  pulled  out,  and  the  body  inclined, 
as  shown  in  the  figure,  stands  13>2  inches  high ;  the  draw-tube  pulls  out 
so  as  to  give  the  standard  length  of  body.  10  inches.  When  placed  in  a 
vertical  position,  with  the  draw-tube  pushed  in,  the  instrument  stands 
only  10)3  inches  high,  so  that  it  can  be  used  comfortably  on  an  ordinary 
table.  This  is  a  great  convenience  in  the  rapid  examination  of  liquids. 
It  is  very  complete  in  all  its  appointments,  is  capable  of  receiving  and 
doing  justice  to  any  accessories,  and  is  contained  in  a  handsome  black 
walnut  box,  with  brass  handle,  lock  and  key.  It  is  equal  to  all  the 
ordinary  requirements  of  any  physician,  student  or  naturalist. 

PRICE— With  Accessories,   as  above  described     -    $35.00. 


THE  YOUNG  SCIENTIST, 

A  Practical  Journal  for  Amateurs. 

ISSUED  MONTHLY.        Price  5O  Cents  per  year. 

It  is  characteristic  of  young  Americans  that  they  want  to  be  DOING  something. 
They  are  not  content  with  merely  knowing  how  things  are  done,  or  even  with 
seeing  them  done;  they  want  to  do  them  themselves.  In  other  words,  they  want 
to  experiment.  Hence  the  wonderful  demand  that  has  sprung  up  for  email  tool 
chests,  turning  lathes,  scroll  saws,  wood  carving  tools,  telegraphs,  model  steam 
engines,  microscopes  and  all  kinds  of  apparatus.  In  nine  cases  out  of  ten,  how- 
ever, the  young  workman  finds  it  difficult  to  learn  how  to  use  his  tools  or  ap- 
paratus after  he  has  got  them.  It  is  true  that  we  have  a  large  number  of  very 
excellent  text-books,  but  these  are  not  just  the  thing.  What  is  wanted  is  a  liv- 
ing teacher.  Where  a  living  teacher  cannot  be  found,  the  next  best  thing  is  a 
live  journal,  and  this  we  propose  to  furnish.  And  in  attempting  this  it  is  not 
our  intention  to  confine  ourselves  to  mere  practical  directions.  In  these  days 
of  knowledge  and  scientific  culture,  the  "Why"  becomes  ag  necessary  as  th» 
"How."  The  object  of  the  YOUNG  SCIENTIST  is  to  give  clear  and  easily  followed 
directions  for  performing  chemical,  mechanical  and  other  operations,  as  well  as 
simple  and  accurate  explanations  of  the  principles  involved  in  the  various 
mechanical  asd  chemical  processes  which  we  shall  undertake  to  describe. 

The  scope  and  character  of  the  journal  will  be  better  understood  from  an  in- 
spection of  a  few  numbers,  or  from  the  list  of  contents  found  on  a  subsequent 
page,  than  from  any  labored  description.  There  are,  however,  three  features  to 
which  we  would  call  special  attention: 

CORRESPONDENCE. — In  this  department  we  intend  to  place  our  readers  in  com- 
munication with  each  other,  and  in  this  way  we  hope  to  secure  for  every  one 
just  such  aid  as  may  be  required  for  any  special  work  on  hand. 

EXCHANGES.— An  exchange  column,  like  that  which  has  been  such  a  marked 
success  in  the  Journul  of  Microscopy,  will  be  opened  in  the  YOUNG  SCIENTIST. 
Yearly  subscribers  who  may  wish  to  exchange  tools,  apparatus,  books,  or  the 
products  of  their  skill,  can  state  what  they  have  to  offer  and  what  they  want, 
without  charge.  Buying  and  soiling  must,  of  course,  be  carried  on  in  the  adver- 
tising columns. 

ILLUSTBATIONS.— The  journal  will  make  no  claims  to  the  character  of  a  "pic- 
ture book,"  but  wherever  engravings  are  needed  to  make  the  descriptions  clear 
they  will  be  furnished.  Some  of  the  engravings  which  have  already  appeared  in 
our  pages  are  as  fine  as  anything  to  be  found  in  the  most  expensive  journals. 

Sipooi^vl    IXTotioo. 

As  our  journal  is  too  small  and  too  low-priced  to  claim  the  attention  of  news 
dealers,  we  are  compelled  to  rely  almost  wholly  upon  subscriptions  sentdirectly 
to  this  office.  As  many  persons  would  no  doubt  like  to  examine  a  few  numbers 
before  becoming  regular  subsoribtrs,  we  will  send  four  current  numbers  as  a 
trial  trip  fcr 

FIFTEEN     CENTS, 


Where  three  or  more  subscribe  together  for  the  journal,  we  offer  the  following 
liberal  terms: 

3  copies  for $1.25 

5      «       "     2.00 

7      "        "      2.75 

10     "        "      3.50 

Advertisements,  30  cents  per  line. 

As  postal  currency  has  nearly  disappeared  from  circulation,  we  receive  post- 
age stamps  oi  the  lower  denominations  (ones,  twos  and  threes)  attheir  full  value. 
Postal  orders  are,  however,  much  safer  and  more  convenient.  To  avoid  delay 
and  mistakes  address  all  communications  to  "  THE  YOUNG  SCIENTIST,  Box  285?, 
New  York,"  and  make  all  checks  and  orders  payable  to  John  Plain. 


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